How to setup Domain user?

Anyone can help me setup Domain users in Mac Pro Server? OS 10.7.4

we have 200 users, should save users' profile in local (not in server).

Who can teach me how to setup?

I tested, if much more users log in iMac same time, log in always fail. and if long time no activity in iMac, since we re-log in Mac, it is fail. Don't know why.

Also, I setup iMac will Iocked out if wrong password more than five times, but we found, one once, iMac is locked out. Do not know the reason.

I think my setup is wrong, so who can help how to setup Apple Domain User?

thank you