Okay, first off, I figure there are 400 topics already about class selection, but oh well, I'm making another. :P
So I will finally now grit my teeth and begin to play Wizardry 6, and I want to take a party all the way to 8. So I am still having doubts about classes and races combos and such. Here is a rough plan I saw that sounded good to me:
1. Fighter - Lord
2. Valkyrie - Samurai
3. Thief -> Ninja
4. Priest -> Valkyrie
5. Mage
6. Bard
Now I am kind of a noob, so I would like to know if this looks good to take all the way through the games. Can I get any input on what skills to focus on too? And if you have any suggestions for the best parties, I would like to hear some ideas. Thanks for helping, I hope this isn't too redundant. :D

I wouldn't take a thief, a bard can handle the Thieving, just give them about 10 ranks in skulduggery to get them started, and let them train on the doors in the start of the castle, and be sure to use your lute in every fight to build your music skill up, and put those nasties to sleep. Then be sure to focus on raising your Tham after you get some starting points in Skulduggery. Legerdemain is just about worthless imo. Several run throughs and not bothered with it. That changes in 7 to some extent but this is about 6.

Instead of making a thief -> Ninja, I'd make an alchemist but try to make them with high stats and then turn that into a ninja instead asap. Since you are going to be rolling with a bard in tow, can focus on his Kirijutsu. If you made them a high stat alchemist to start with, that will give them some head way on alchemy skill and spells as they start out as a ninja. Stat level ups are random, so be sure to save before leveling up and get as many stat boosts as you can for this character until you get them into ninja stat range.

Valkyrie is a great class, and so is Sam for 6 and 7. Valkyrie will get access to a b.a. lance later in the game. Consider keeping it a valkyrie or making samurai -> valkyrie if you are wanting Kirijutsu on your Valk. Valkyrie really is an awesome class as it is solid throughout 6 7 and 8.

If you are patient, try to make your Lord fresh out the gate, I know bonus rolls can be quite boring to roll, you can step into madgod's domain and get his Forge Editor to speed up getting high bonus rolls. Try to resist the temptation of messing with too much as it is your virgin voyage into the depths. These party suggestions are just my own suggestion, and what I would probably do if i were looking at playing with a similar set up. Hopefully this helps.

-Edit -- I'd consider turning your mage into either a bishop or an advanced class fighter of some kind later, I don't usually find the non elite casters very useful, but that's just me. And thinking about it, if you don't want to run 2 valkyries, consider making that priest -> valk into priest -> monk instead. Monk is great empty handed, but there is a rare rare bo that can drop close to the end game that is very powerful too.

Okay, this is my revised party layout.
1. Lord
2. samurai- valkyrie
3. alchemist- Ninja
4. Priest - monk / valkyrie
5. Mage-bishop
6. Bard

Now the question is, when do I change classes?

And I'm uncertain about what races to make them all. :/

Well, that alchemist -> ninja should be as soon as you possibly can. Like if you can turn into a ninja after 1 level up do it. A little technical babble to this being there is a 'hidden' stat called miss chance that is dependent on level ups and class. Alchemist get one of the lowest miss chance reductions on level up something like 1d3, ninja get 1d4+2 to their miss chance reduction. This stat stops accumulating at 20 character levels, so if you had to level 4 or 5 times as an alchemist you'd get 4 or 5 levels of 1d3 miss chance reduction then 13 or 14 (don't think you even get miss chance roll for level 1) levels of the 1d4+2. Nothing SUPER critical, but it is worth keeping loose track of in the back of your mind while moping around.

A decent early place to toy with class changing though would be in a place called "The Bell Tower". You'll know when you get there, as you have to swing across a rope hanging out of a bell and each time you do you get in a fight with some bats. This is a decent and easy low level experience grind spot, and you can control your level ups fairly easy, saving before each swing on the rope. If this is a bit too slow for your liking, go to the downstairs area of the first part of the castle and go down another flight of stairs there into a long'ish hall way. You can fight some reasonably tough monsters with a bit more experience to them. Some say level 7 is where you want to start changing classes, I feel 5-7 is a good spot to do it, but I've also waited as long as the Hall of the Dead which is considered the end of the midgame before really buckling in and doing it up. Just be sure to have some of the early essential spells from a previous class before switching over to your new class.

Some of the better ones would be Heal Wounds, Cure Lesser Condition, Bless, Dispel Undead, Sleep. If you get pretty high skill points in your level ups you might be able to get Cure Poison and Sane Mind too, but those are fairly high level, and you might not get those before you get into your class changing. If you want to cheese it hard, you can hang out in the Hall of the Dead later, as there is a fountain that will replenish your hp stamina and magic all together and grind there, and change classes and getting decked out with all kinds of spells. This gets extremely boring though, and trivializes late game, but I have done this before in the pursuit of having a beefy import party. Don't let me bore you though. The game is totally beatable without class changing if you decide to run like that. Anyhow, I hope my ranting helps!

Yes, it does, thanks! :D If I can ask one more thing, what would you suggest my races should be?

Well, I like a good mix. Mook is pretty good at everything, and they are like Wookies.. Everybody loves Wookies, yeah?
For your alchemist -> ninja, I'd go Faerie. Other than that, I usually take a mix of humans elves and Felpurrs. You could drop that and take a Dracon though, Dracon get a great breath weapon attack that destroys early monsters. 2 Dracons breathing probably would wreck but I never really ran with that before. I dinked around wizardry 8 with a dracon though and had a good laugh.

Rawulf is supposed to be great for the preistly/lord situation, and get increased mana regeneration supposedly. Never really noticed it mana regen is slow. I think Lizardmen get the best melee oriented stats, and slow int/chr/piety growth, but I never bothered making a Lizardman before.

Really, I'd recommend just running with what you are comfortable with, can't go wrong. The only thing I'd highly suggest out of them all would be making the one who is going to be a ninja a Faerie. If you take a Mook, they get great mage stats, and make good Samurai as well.

Only race thet gets bonus to mana regen is Fairy, IIRC.

Other things to consider.
Go Priest -> Lord
and Priest -> Valkyrie with your two first characters. Make sure they get enough Bonus Points that you can switch to Valkyrie as soon as you enter the castle. For Lord you may have to wait for some stat increases.
That way they get a permanent bonus to mana regen that can be important.

Also note that character level is used in just about every combat calculation, so I'd only class change once and as soon as possible. You may find your mad martial arts skillz awails little if your character is too low level compared to the enemy, and characters who got their final class too late, will be in a world of pain against certain high level enemy spell casters.

That Caster class -> primary class change is a great tip. Mana regen is set in stone at the start of the game and is dependent on your starting class. Every little bit helps, because it does regen slow for the elite classes. I think you're right. I think I'm getting the Rawulfs mixed up with the dog race from a demo of a game I tried a while back called Grimoire. Would explain why I didn't notice it kicking in.

Your party is fine. There's no noteworthy difference between the races except fairies who have armor/weapon restrictions but get some resistances and a faster mana regeneration rate and dracons who get a breath attack.

About your characters:

1. Fighter - Lord

Fighter, Lord and Valkyrie are the only classes who can wear the heaviest armor and use the biggest weapons so you'll want 1-2 of them.
Starting as fighter and switching to lord later can be advantageous. You can't put skill points into theology at creation and loose a few XP for the first class but you get 1-4 extra miss chance reduction, can put some points into scouting and start with 1 less point in int,pie,spd,per and use the 4 points for starting with 16 str (more carrying capacity) or 16 vit (faster mana regeneration rate) instead.

Start as fighter, pump all skill points into scouting, when you reach level 7 (or at level 8-10 if you haven't the necessary stats yet) switch to lord and put all skill points into theology.

2. Valkyrie - Samurai

Samurai are very good in the beginning and the great in the last third of the game when you've found some special gear. You'll definitely want one in the end game.
Thaumaturgy or kirijitsu are the only skills worth raising for a samurai. Maybe ignore thaumaturgy totally or raise it 18,36 or 54 and put points only into kirijitsu afterwards.

Valkyrie -> Samurai will work, maybe start as dwarf with a roll of 18 and 1 int,dex,spd less than needed as samurai, use a sword to get up the sword skill by fighting and switch at level 3-6. But what do you expect to gain by the valkyrie levels ? Pure class Samurai works well too.

3. Thief -> Ninja

This works very well. Opening locks and identifying traps will be problematic without a thief, put all skillpoints into skullduggery and switch at level 5 or so. Fairy is the best race for ninja (you can start with lower pie than needed for ninja) but other classes like dracon work too.
As ninja I'd raise alchemy to 18 (or maybe 36 or 54) and put all other points into kirijitsu. Train unarmed (as ninja) and hiding (from the beginning) by using it.

4. Priest -> Valkyrie

Works very well. If you have a dwarf with a roll of 18 you can start with both 16 str and 16 vit, one less pie, dex, spd than needed for Valkyrie, put all skillpoints into theology and switch class at level 3-6.

5. Mage

Roll a fairy with 16 vitality and put all skillpoints into thaumaturgy for a lot of spellpower. Switch to bishop in W7.

6. Bard

Thaumaturgy for spellcasting. Maybe put points into skullduggery first if you don't have another thief and don't want to rely on the knock-knock spell. Take a female and use your instrument a lot.

FWIW, I just started playing Wizardry 6 for the first time, and here's my party:

Cerberus - Rawulf Lord
Gary - Lizardman Monk
Ancala - Dracon Valkyrie
Thelonious Mook - Mook Bard
Dawn - Elf Bishop
Mesmer - Human Psion

I'm not planning on changing classes at all, so there you go. Having fun so far.