2 stud or not to stud

Wanna hear everyones thoughts on what you look for in a stud dog. What qualities or traits stick out in your mind that seal the deal when you look for a stud??
Then if you have the stud what do you look for in the gyp??

Hers a few examples:
Does both dogs have to belong to you or friend or family?
Both dogs tested for disease or genetic defects?
Do they both need to be "proven" stock?
Do you ask for a signed agreement before breeding?
Does the owner of the other dog affect your choice??

Just another thread I saw on another board and wanted to bring it to our board for discussion.