[ryanto]

I've found the best way to know if I'm going to work well with someone is to have previously worked with them before. Look for people you've enjoyed working with, be it a co-worker, classmate, someone you've worked on open source with.

Things that I think must exist between cofounders.

* You must like and trust each other.

* Make sure you are able to be candid with each other.

* Know each others weaknesses. Really another way of saying have realistic expectations.

If you have no prior work experience try working on a small one-off project to get a feel for each other's working styles.