Things to look out for:

• He must WANT to be in a relationship
• He must be ready for commitment
• No more social butterflies
• MUST see how he deals with problems
• Check family background and determine if he is spoilt
• MUST have gone through hardships
• He HAS to care about something, and can't be to nonchalant about EVERYTHING
• He must have fought for something before
• Someone who can talk shit with me about anyone who's pissed me off (and say FUCK THEM :D)