I'm not typical because for me it's purely a secondary income source. Thus, I'm not as "straight-edge" about the work making the world a better place or making people feel wonderful while using X. If that happens as a by-product, I'm amped... but for me I'm generally looking for any combination of:

A) Jobs that enhance/build/support my network. Real example: A CEO of X company needs a new powerpoint for a huge speaking engagement he's doing and was sent to me by another CEO I've done work for in the past. Yeah... I hate PPT... but I'm not turning down that kind of networking opp. A notable bonus, when it's something for a founder/c-level exec... you always get paid right.... and always on time or quicker.

B) Work for previous clients that have always come to me, have always paid on time, etc. Not all the work is portfolio worthy... but it pays and they are reliable as hell.

C) Jobs that I WANT to do. Since it's a secondary source of income... I've turned down gigs that simply aren't interesting to me. The fact is, if you aren't pumped about it for some reason... the work quality will suffer. Sometimes... even 2X your normal rate simply isn't enough incentive to keep your mind in the game. I always walk away from these jobs. If you don't care, or if you don't benefit in some way or another... the work will be shit... and it WILL bite you in the ass later.

D) Projects that fit my schedule (within reason). Because it is a second income source... and because I have a young family... I refuse to burn myself out on crazy deadlines.

E) Projects that meet my rate/price. Too expensive for them? I'll suggest other people they can contact. Time is money. Your work has value. Never de-value it.

Just the feeling you get from meeting them; first impressions count and if you don't gel then you get the sense that it's going to be a difficult relationship.

We deal with people and it has to feel right. If they are on board and trust you as a professional then great hire them as a client.

You want a project to be as frictionless as possible and the biggest factor in this mind set is another human.

Money and scope helps but I'd rather deliver something the client is 100% behind than delivering something fraught with constant battles.

I'm not sure what replies you are hoping to get, we all have different things that motivate us to do the work we do and we are obviously going to look for that in the clients we favour.