[how to] Customize the signup process

Hi,
When people signup to my site, it ask for :
Username
Password
*A password will be e-mailed to you.

1. How can change that for people to choose their own password right away ?

2. I also want new users to be held for moderation & approved by the admin : How can I do this ?

3. I would love to add a 3rd field when people signup and wondering if there's a doc somewhere that can show me step-by-step guide for doing so ?

Username
Email
Your current ID <- what I want to add

*and display the text of this field on the profile page

Thanks for any tips you may have