I run Shiamano Spd-sl standard pedals onto Shimano Rd64 shoes, because they were cheap, fitted me well and were readily available.
Really you need to hit up a bike store and them out, the different brands that produce clipless systems that come to mind are:
Shimano (spd and spd-sl), Look (keo range for road cycling), Speedplay, Time, and Crankbrothers (eggbeaters)
Things to consider are:
-How easily you can clip in/out vs how likely you are to unclip accidentally (which is really bad if it happens apparently, has never happened to me though)
-platform size (a small platform puts more pressure on a single point of your shoe, meaning it will have more stress in certain places, and probably won't last as long, small platforms are light though, if you're a weight weenie inclined kinda person)
-availability, if they're hard to get, chances are it's hard to get replacements parts (cleats especially) which can be a PITA if you need them urgently, ie plan ahead...
-price (well, yeah, to few, money may be no object, but for most, it is certainly a large factor, it's a huge factor in what I run)
-walkability of the cleats (depends how much you need to walk off the bike, I have to walk through train stations, up stairs etc in my cleats, and it really sucks. big road cleats are awful for walking in....
-probably lots of things I've forgotten,...
The other thing I would think about is your knees..
Some folks complain that Crank brothers and speed play let your foot pivot and that bothers there knees.
I like my egg beaters and my wife also likes her Crank brothers candies as they are easer to get in and out of.