I've read if I give Ian's list to Diego, I cannot (or may not be able to) join the New Camp after joining the Old Camp. Is this true? If so, what's the proper method? I can't seem to get inside the castle without giving Diego the list.
Also, if I join a camp before completing all the quests in each of the camps, do I miss out on those for later, or are they still do-able?

You can't get inside the castle before completing Diego's test of faith (the list thing) and gathering enough support for the relevant NPC's from old camp (the rep side quests).
There are quests that can be done regardless, others cancell each other out depending on which faction you join, i think.

But is it still possible to join the New Camp later if I give him the list and join the Old Camp?

I don't think so. Giving him the list it's basically choosing Old Camp.
And it's probably a good idea completing as many side quests as possible before actually joining one of the factions/camps.

Hmm, I know it's possible to join both, though. I will have to do some more research, then...
Thanks for the advice. :)

You're probably thinking about the mages there.
As for Shadow (old camp) vs Merc (New camp) i don't think you can't have it both ways ;)
You can however go with Old camp (Shadow) and later on join the Water Mages in New camp.

I think i was wrong and that it actually goes like this :
If you join old Camp, you can become a Fire Mage or a Guard.
Later on, you'll get banished from Old Camp.
At that point, you can become a Merc if you were a Guard or a Water Mage if you were a Fire Mage.
Hang on a bit, i'll check that WoG page and edit my post

Spoiler. :(

Dude, spoilers! :o

:(
Oh well, I downrated that post, so take that! :)
That's what I thought. I seem to have gotten confused by the guide I read, it said to not give the list to Diego, but I think they meant so you could finish all the other camp quests first before proceeding.
And yeah, this game is deep as hell. Love it.

Heya Arkose. I'd like to thank you for helping me get into Gothic. :)
I'm a certified addict now. Glad I got into it before Risen.

[Force Persuade] You didn't see that spoiler...
Seriously man, i'm really sorry about that.
Some parts of the game can get a bit confusing if you're trying to do everything and trying to keep your options open at the same time. But you're right, there's depth.
I really like the Gothic universe, and now it seems the Risen Universe aswell. Just have to wait for the price drop on that one :(

Well you're kinda groveling so its okay. :D
I do haaaate spoilers though. But this doesn't seem to be a HUGE one. If it was I'd probably never forgive you! :)
Yeah it can be confusing but I love it for that. Love love love.
Risen is totally in the Gothic universe -- I will always think of it as Gothic 4; it's only legal nonsense that it's not called that. From what I've read and seen...seems Arcania is really falling behind...it's been years and they've got little to show for it. I checked the Arcania forums and apparently JoWood is doing a poor job of keeping fans updated and stuff, too, to the point where they're demanding info. Doesn't seem like Risen took that long and it's damn fantastic. I mean, I hope Arcania is good in the end (two Gothics! :D), it just really doesn't look like it.
Don't wait on the price drop! It seems so worth it. They deserve all your moneys. :)

After finishing the demo for Risen, i actually went for my CC to get it. But the $75 price tag made me back down. It's too much for a game. But i'll consider your words of wisdom ;)
But the demo made quite an impression on me. Specially how good it looks, and how smooth it feels.
I haven't been tracking Arcania, but i hope it turns out ok. There's no such thing as too many good Gothic games ;)