Here's what I look for when assessing whether to invest my time coaching a young entrepreneur:
My answer might be bias since I am an entrepreneur. Looking back, here are top 3 qualities I think are important:
If you want VC perspective, Mark Suster of GRP cover this topic at his blog here: Both Sides Of The Table Hope that helps.
I will look for someone that shows passion for our product or service, someone who shares similar goals and is willing to make some sacrifices to achieve these goals. Also, very important I think, I will make sure that this partner has experience or knowledge in an area I don't.
That is the foundation. You don't really need much more.
(By "intelligence" I don't mean genius or brilliant. It just means the person can function well in the domain we choose for business)
I left a partnership because the person who founded it with me decided that he could double bill clients and justify it because he was "twice as productive as other developers"
Domain knowledge and other things can be learned. Integrity and work ethic are key character traits vital to a company. Just about anything else can be learned/taught.
As proof, take a look around at the businesses that exists today. Many were started/founded by people who are no smarter than the others who failed.
Successful businesses "make it" in spite of strings of mistakes. There are plenty of examples of super smart people failing miserably with their ventures.
Here's an "uncomfortable" topic: If you will get materially involved with your partner (and most likely you will) ask him/her if it would be OK to check their personal credit report. There might be some items there that could be explained. However if you see red flags and the partner can't offer sound explanation -- watch out. If this person can't run his personal "business" what makes you think he/she will be capable of it in your mutual partnership.
Many people are very good with words; you need to check the facts.
This method is also a good way to see how transparent your future associate is willing to be with you.