I thought it might be nice to have a thread to list Hints and Tips on how to play Giants without getting nearly through a level and then dying only to have to start over again.
Disclaimer: Some of these may be considered exploits so take them for what they are.
General Tips:
1. Always keep a health syringe in your inventory.
2. Always use your health syringe (H Key) when you see one drop and can get to it and pick it up to replace the one you just used.
3. Use the Sniper rifle to take out enemies from distance. (E to use zoom, and Z to set zoom level).
4. Always scan the horizon for turrets and then take them out from distance. The sniper rifle is a great weapon for this.
5. Go back to the shop to heal, and ammo up again.
6. Strafe around your enemy as you shoot at them. (A & D keys)
7. Always use proximity missiles on the flying Reapers. You can shoot this from long range and it will not explode until it is near the target. This weapon is much less effective on ground units.
8. Stay on the mountains and sneak up on enemies. Also, it is a great vantage point to hunt from. Remember you can still be hit (splash damage) if you back up from the edge (cannot see the enemy) but are still close to the edge of the mountain.
9. Place mines on the set paths that the enemy takes. Try to pick up mines dropped and spread them around the area, but remember quickly use the one in your inventory first.
10. Always go for head shots; as many times, depending on the weapon, it is a one shot kill.
Next I will talk about Base Building, and maybe add in a few more tips.

Building Bases
1. When building bases you have to build a Shield Generator first, and it is not a bad idea to upgrade it directly.
2. Only assign just enough Smarties to build what is needed. If you have enough food and Smarties you can send out multiple groups to build different things at the same time.
3. Build defensive walls right after the Shield Generator.
4. To upgrade individual wall sections click on that section when on the Build Pad.
5. Always upgrade the sections of the wall facing the direction that the enemy is coming from first.
6. Remember, flying Reapers will try to take out your base from the air. Use either Proximity Missiles or (if Delphi) use the Arrows that target multiple enemies at once. They are both very effective.
7. Make sure as you search for Smarties to build your base, pick up Vimp meat or kill enemies or Vimps if you are Delphi.
8. When killing Vimps for food only kill what you need. If you kill most of the Vimps (say you leave 2 or 3 alive) make sure you kill the last few as well. They will not respawn unless they are ALL dead.
9. Place mines in the pathways that the enemy will travel it will save you running in too many directions at times.
10. If the enemy steals Borjoyzee make sure you kill the enemy and simply touch Borjoyzee to return him home.
11. Once you get the needed Bomb, or Spell you no longer have to worry about the base let it go even if it is getting killed.
12. You can pick up the Repair Tool/Spell to fix your base. The Repair Spell has 3 uses and then you need to pick up another one.
Hope this helps on base building for some that find it rather a challenge at times.
Next I will give some ways to avoid fighting at times...

Avoidance, Exploits, and Misc. Tips
You can avoid enemies at times and save fighting if you are not doing all that well. Read and apply these at your own discretion.
1. On missions that do not require all enemies to die; bases and enemies can be avoided by going over mountains.
2. For mountains that look to high to jet over follow these steps.
a. Look for a less steep area of the mountain.
b. Then look for crevices with little angled areas that you may be able to rest on for your trip up the mountain.
c. Next jet up the crevice trying to conserve energy. Try landing on less sloped areas or keep pressing the forward key to try to keep your character in place while your jets recharge.
d. Keep trying until you reach the top or try a different area that is less steep or has a resting spot on the way up.
You can do this with each character, Baz, Delphi and Kabuto. Kabuto is the easiest to do this with.
With this method you can jump past enemies and conserve your health, but it does take away from the game a bit.
3. Mountain tops can give you the element of surprise and let you kill enemies that otherwise would be difficult.
4. Try all weapons on different enemies. Some work better than others on certain enemies.
5. Once again, try killing most things from distance or at least causing them damage making them easier to kill when they arrive.
6. Always kill enemy bases first when you go into an area. Once you do that you only have to deal with those that are still alive. Also, kill the Missile Soldiers first before other enemy units.

This goes for enemy launchers and pop-up dispensers (not sure what the real term is) where the enemy comes out from to attack.
7. One of the best weapons for Delphi is her Sword. You can zoom up to the enemy and swing at just the right moment and kill, many times with 1 hit and normally a maximum of 3 hits.
8. For some reason when you get right up on an enemy they seem to miss you shooting at you as you hack them. not always, but a lot of the time.
9. Do not forget when playing Kabuto, if you pick up an enemy or Vimp (Right Mouse Button) and then hit the X Key Kabuto will impale what he is holding on his frontal spikes which can be saved for later.
Plus this just looks cool if you hit the F Key to view the character from the front.
I hope these tips help some of you playing and if anyone else has tips please post them so that others will know.

Anymore tips from anyone, or has anyone tried these out?

Well, it's an impressive list, and I have used some of these strategies when I played the game many years ago. Here is a strategy I used for the Mecc base building portion of the game:
The best thing to do when starting out is to make sure you have ALL of your Mecc buddies following you (should look like a flying V formation). Each one of these Meccs are able to pick up Smarties and Vimp meat, so use them to your advantage. Yes, it leaves your base defenseless for a while but you're able to build up a base faster and more efficiently.
What this essentially does is makes sure that you're able to pick up most, if not all of the Smarties on a map in one hit (plus a lot of Vimp meat).

Thanks for the tips
Here's a question, how do you get the Kabuto babies to attack? I can get them to grow by bringing them to vimps, but I can't get them to attack anything even if they're standing right next to it.
Edit: Nevermind, figured it out, you have to look at the offspring and hold control and left click. Kind of annoying, but whatever, you don't really need them.

Use these tips and add your own to help others with this game.

Are you talking about the early Mecc mission where you have to save the Smarties dangling from the cliffs? For that you have to get close enough to pick them up, then move to the dropoff zone on a small, nearby island (I think it's marked with a big Smartie face). They should jump off automatically when you get there, and then you can go pick up more.

They never seem to jump off automatically, but I'll check my map again, because I thought it was the small island in the middle that I had to go to.

No, its not in the middle, its near the hanging smarties but not in the middle

For people interested in playing online, here are a few starting tips for Mecc vs Mecc games,
• Typically, the weapons you're going to be using the most will be proximity missiles, homing missiles, and rockets.
• Proxies are more or less your bread and butter weapons - because they explode when they get within a certain distance of an enemy they're good against enemies that are not on the ground - that, and the fact that they don't require any lock-on time (like the homing missile does) makes them the best choice for anti-air.
• Rockets should be used against grounded enemies whenever possible due to their higher damage rate and larger splash radius.
• Homing missiles require your enemy to either stop shooting and fire a flare, dodge (by jumping out of the way just before the missile is about to hit the ground), or if they're using a shield pack, absorb the damage. If your enemy is in the air, you can fire a homing missile and follow up immediately with a proximity missile - if you're fast enough both missiles should hit within a second or so of each other.
• Sniper rifles do great deals of damage, but I can only think of four or five people that have been good enough with them to use them in the middle of combat against another player. In Defend the Base game modes, they can be used to deal a large amount of damage to enemy structures, and are similarly useful against Kabutos in three way games.
• Mortars make large explosions and are very rarely practical to use against anything that is capable of movement.
• Machineguns should only be used against buildings, or (if you're feeling lucky), Kabutos.
• Relying on solely on your jetpack won't get you far online... because most weapons do not harm you by default in Giants, you can use explosions from rockets, grenades, and mines to help propel you and keep you airborne - this will allow you to move amazingly quickly over large distances.
• The jetpack upgrade is probably the best idea for most people in terms of backpack items...
• ...but if you can use it properly, and learn the proper strategies associated with it, the Shield pack will make you near unstoppable. Playing with a shield pack is very distinct from playing with a jetpack upgrade however, and has a fairly massive learning curve.
• Proximity missiles explode when they get near enemies - but they also explode when they get near enemy buildings and deployables. If you're grounded and an enemy shoots a proximity missile at you, you can toss a mine ahead of your into its path, causing it to set off the proximity missile (and destroying it in the process, obviously).
And... that's all that springs immediately to mind. Some of this is applicable to three way games as well.

Well, thanks for hints'n'tips guys, but still a have one serious quiestion.
Some of my leds are dying. I see them on the map, but I don't see their bodies.
I can repair only mates with still alive and running here'n'there, but what about others?

I am not sure what you are asking, and I am not sure what "leds" are either.

We have Meccs Team, time-to-time they dying "I need to rest for a while" & etc. After some time they come again back. But after sometime they dying like forever. I can see their icons on the map, but in-game there is no meccs on the screen.
Also I see repair guns, here and there lying just like that on the ground ( but not in place where my comrades are died).
I've tried to run here'n'there around on whole camp with activated repair gun: around repair guns, around place where icons of Meccs. Nothing.
Is there anyway to ressurect them? Or I need to fight alone till new phase of the level?