How do I add or delete user accounts in Ubuntu?

I know that the "useradd" command could be used to do this, but I hear that Ubuntu has some other command-line tool and some GUI somewhere, either one of which I could use to make adding, deleting, and otherwise managing user accounts much easier and less error-prone.

(An ideal answer will also mention the standard stuff a sysadmin should do immediately after creating a typical new user account -- using Diceware to generate a new memorable password, etc.).