Matchmaking is a process that most singles are forced into at some time or other. Personally I think that it's great that friends partake in this process for their single friends. Sometimes it is extremely successful (a friend of mind was matched into a blind date dinner in the opposite island - now married and extremely happy), but most of the time it isn't, but that's fine as long as the matchmaker shows a little bit of sensitivity:
1/ Put some thought into it - just because your single female friend (SFF) and single male friend (SMF) are both fancy free, doesn't mean they will fall for each other. They are after all single for a reason, fussiness is probably it. However if you follow rule 2 below you can put in less thought as it won't really matter.
2/ If you are planning to match your SFF and your SMF at a party/dinner/BBQ, then please only tell one party to the match. It is just incredibly awkward if both know about the potential match. My suggestion is that you tell the man. Woman generally like to be pursued and men like to pursue*. Of course some discretion can be applied here depending on their personalities.
3/ Do not under any circumstances tell other people at the party about the matchmaking. You may have got all excited by the prospect of fixing up SFF/SMF and think it's all terribly fun, but an audience can be rather humiliating.
4/ But not telling either party to the match is probably the best plan - just organise a party and see what happens.
* Not sure the rules of engagement for the gay and lesbian matching, but I'm sure it's more fun than the heterosexual dance that goes on.