Well really, you'd have to look around and find out if there's a basic set of "things" that you'd normally need access to, to be able to "get on".
The whole principal of linux is the same (well pretty much) as unix. That's why linux is described as "unix like" or "desktop unix".
We are all aware that it's quite a bit more than that, but if you've had mainly experience of W98 and similar, then you've not so much been spoiled, but ruined. IT habits wise that is, because it's only been since xp (or NT as a commerical user - don't know about Me so ??) that you've started to have similar protections i.e. with XP home, when you install or just basic setup you'd automatically have root priviledges, whereas if you'd done a multi user setup, then the admin account has the root priviledges, and the user account can only do "user stuff".
So, you'd have to find out about whether there's a list of suggested stuff that you'd need to have access to, to work/play as user. It sort of becomes second nature after a while.
For instance, the gentoo docs suggest that when setting up user accounts, you do
# useradd -m -G users,wheel,audio -s /bin/bash john
for an account for the user "john".
Don't follow the last bit (/bin/bash) someone might be able to explain that bit, and the -m -G bit's should be in the man page, but the other bit is saying to put user john into groups users, wheel and audio, users and audio are self explainatory, the wheel bit, thats important because without that, you can't do "su" commands.
If you open the editor you like and look at /etc/group, you should see the list of stuff that the users (user and root) can use and that some processes need to get access to as well.
Sorry if that doesn't seem to make sense, it does to me, but having reread it, I can't think of any clearer way to explain it.