Define inexpensive. I usually spend $300-$400 each for less-than-exotic wireless mics. Is that what you have in mind?

Plus -
Do you mean hand-held cordless or a headset mic with belt transmitter pack? Or maybe, from the last part of your post, you mean radio mics on a stand, just to avoid cabling?

Also, if these are to be handheld mics, what type of talent will be using them? A breathy female, a screaming rocker?
We all have to deal with wireless mics at various times; they are a necessary evil, and the low-priced ones are especially evil!
I don't know what frequency bands are permitted in other parts of the world, but in the States, you are pretty much delagated to UHF bands that are now competing with other forms of radio transmission. This is something that others (like Boswell in the UK) may be able to clarify if you are over there, for instance. Does your head hurt yet?
Also, I meant to add this:
You asked how to connect them. The receiver for most of them is a line-level source, so you'd plug it into the line in on your mixer's input channel.
Many receivers have an XLR output, designed to plug into the XLR MIC input on a mixer. WARNING!! Some of the cheaper systems' receivers that have an XLR output do NOT work properly IF the mixer has phantom power engaged!!! In fact, I've seen that KILL a receiver, not cool. With these systems, it's probably best to not use the XLR, just the 1/4" line jacks if you need phantom power to be on for other mics...

Hey its for a hip hop group. But I gather from reading your replies that wireless mics are not better then non wireless mics. We need something to do shows with..

so how much are you able to spend on this setup? In addition to wireless rigs themselves, you'll want to get a case or rack bag for hauling things around - that and a few short mic cables for hooking up - an outlet strip so you only need one one power plug.

gotta' have a budget to work with.

No, I have never considered wireless mics "better" than wired ones. They certainly don't sound better than the equivalent wired versions, IMO. Maybe for hip-hop performers, who always spec the wireless models for the gigs I ocassionally do for them. I think that they like that "over-saturated" sound you can get from "eating" a wireless.
So it's like Zem and the others said, what type of budget?

Plus wrote: Hey Im looking for a good but inexpensive cordless mic set up. I need 3 mics for live performances. Im really very new to cordless mics, so what do I need to look for? Any help would be great. Also when at an event how and where do you hook up the cordless mics?

Well, you are in for a shock if you live in the USA. In 2009, most budget wireless mics will not work, or will not work well, in populated areas. The US government sold off the 700MHz band. That is forcing a crap load of traffic to go lower or higher. Higher is more expensive right now.

What does this mean? If you have systems that will travel, you will need to be buying dual receiver or diversity units, with selectable frequencies. All of this low-end crap at the music store will not cut it.

People ASSumed that someone in the government was actually doing their job, representing our industry. It wasn't until Shure and some other companies went up to the hill with the NFL and other sports folk and said, "If you like to watch football, NASCAR, etc, you will pull your head out of your crack! No wireless, no sports!" That got their attention, but not enough to change things completely. What the FCC did was mandate that the citizens of the US purchase new technology. Then it madated broadcasters to spend millions to accommodate it. It was paid billions by auctioning off frequencies to telcoms. Who knows what other under the table actions were taking place.

The FCC is doing tests now on the next gen technology that is to detect a unit in use in the "white" band, and work around it. The stuff is not working. Three systems tested have failed. What this means is that whoever has the strongest signal wins. Whoever has FCC licenses to broadcast at a higher power level wins (that aint Joe's bar band). So, it is going to be a time to get reaquainted with wired mics if you cannot afford to do wireless right. Right is not cheap. Cheap means poor sound, poor range, poor integration with multiple units and users, unless you are just out in the absolute middle of BFE.