Custom Login Page

I am new to wordpress ms. I have went through a few basic tutorials about creating plugins and widgets. So far, everything seems a bit mysterious.

I love the idea of allowing users to create their own sites on demand. My problem is that I need to gather a little more info on the user during the registration process. It seems like a simple task (add some new fields and and some new database fields to hold the data). But I can seem to wrap my head around how wordpress works.

Since I don’t want to use the wp-signup.php, what should I do?

Should I?

1. Make a copy of the wp-signup.php and modify it to what I need?
2. Use/Create a plugin to do the job?
3. Hold my head under water until the pain goes away?

For instance, I want to ask for the name of their business and phone number. I just can’t figure out the best way to do it. I have been programming in php and jquery for years, but all this stuff about hooks doesn’t make sense to me. Please help