Case in point: A few years back I dipped into my Rolodex to help a friend make connections for her new business (a marcomm agency). After reviewing the strengths of her business I was able to make some strategic introductions for her. From those relationships her business has flourished through direct and referral opportunities.
I know most of my readers would say they are already doing that, but there's one more step to really make your generosity pay off.
That last step is letting go. Once you have made the introduction, stay out, completely out, of their budding relationship. If something goes terribly wrong, you'll hear about it from one of them. If it goes wonderfully right, then you'll hear about that too. Instinctively you may want to 'care-take' a relationship you initiated along the line of, "But what about my reputation? How can I protect my reputation if I don't make sure it works out?" Let me answer that with a couple of thoughts.
One, you can't make anyone feel anything. Both people introduced are going to make up their own mind no matter what you do. More importantly, the more you stick your nose into what goes on between them the more YOU WILL be held responsible if it goes wrong. By staying out of the way your reputation can continue to be measured solely on your willingness to help and your personal interactions with each contact. It's OK to let them be responsible for what goes on between them.
Second, if you are concerned your contact will not get along with the person you referred, then shame on you for making the referral in the first place. If you are too insecure not to meddle in the affairs of others then don't make referrals.
Matchmaking is a good thing. Do it as often as you can. Micromanaging is a bad thing. Do it not at all.