Need help to Make user registration a two-step process

I have an partial Wordpress website that needs to be completed. There are about 15-20 things that want to be done however I want to first start with this one example to see how well we are able to work with each other.

The website presently offers a 'user registration' functionality. Therefore the user can create an account by entering 20 fields - like name, location, email id etc.

I would like to modify this registration process to two steps - user registration and profile creation. Therefore 20 fields are still captured but in the following fashion-

Step 1: User registers on the website by entering 8 fields. At the moment user registration is complete and the user can continue to profile creation or the user can create a profile whenever he logs in later.

Step 2 - User creates a profile by entering extra 12 fields

Desired Skills are MySQL Administration, HTML, PHP, WordPress