Building Healthy Credit VS. Creating Bad Debt

Often when I am talking with clients looking to buy in the near future, the subject of credit comes up.

What are some ways to build healthy credit when starting with no credit?

How can you be sure you don't have to many lines of credit open. Lenders like to see money borrowed, but where is the point where healthy credit building becomes climbing into debt?

Please post your thoughts and suggestions so that when people are working with minimal credit buyers, we can give them healthy advice.

Josh