Cannot get users to login to Terminal Server

I have to setup users at remote locations to login to our Terminal Server, and it's driving me crazy. I setup a new user in AD, put the user into Remote Desktop User group, as well as Terminal server users. Also put into Allow to Log On locally. All to no avail. After a while, it doesn't even let me login as the Adminstrator, even though that account was working a short while ago. I think I have tried a hundred different things to try to simpy get a user account to access this server. ideally I would like to create some kind of group, that when I add a user to that group they gain access to this server. Can someone point me to some simple guidelines to setting up remote users to login to a Terminal Server? It would be appreciated. Thanks.