I think "all of the above" is a good answer. There are many different types of blackjack teams and each requires different skills. Every team will be looking for a specific type of person. They may find that person at work, at school, at a blackjack gathering (BJ Ball, Green Chip party, Holloween Ball, etc.), in a casino, or even a family member. Al Fransceco found Ken Uston at a cocktail party (or so the story goes).
The most important factor will be finding someone smart who you can trust with your money. I have had good success training close friends and family members, but it can be very handy to find someone who already has experience. The specific requirements you are looking for will vary depending on the type of team you are forming.
-Sonny-