Nobody has the exact same criteria but these come up time and time again in reviews and discussions.

Wanna Switch? - Clicky or Quiet, Tactile or linear? - The switch you choose is probably the most important decision you will make. A Clicky keyboard is fun but can get LOUD. A sharp tactile keyboard sounds good but if it's too stiff for your fingers maybe you should have gone lighter. There is no one perfect switch for everyone. And it's fun to try new ones!

Build Quality - This is pretty subjective. Some people equate weight and plastic thickness with durability. Details such keyboard feet that don't collapse easily or slide around, thickness of cable, and plastic finish are other clues. This is one of those things that you can't see in pictures so have to rely on reviews by others. Don't get scared off by one bad review!

Keys - Since this is where "the rubber meets the road" you want durable keys where the lettering does not wear off. Often though it's a complex tradeoff between looks, durability and cost. And in the end alas all keys will wear down nice and shiny (even though you probably won't care if it takes decades of heavy use, which it does for some materials). N-Key Rollover Capability - Any keyboard can recognize anywhere from 2 to 8 keys at one time. This is fine for general typing. However MOST keyboards will fail with certain 3 key combos and this becomes important to gamers (the keyboard is called 2KRO because only 2 keys are GUARANTEED to be recognized at one time). If a keyboard is 6KRO (6 keys guaranteed) and not NKRO (all keys on the keyboard can be pressed at once) don't get too hung up on this. You only have 5 fingers on each hand!

Aesthetics - Your choice. Everybody likes something different. Spend a bit of time thinking though if you are the type of person that likes to keep a keyboard clean. If you are a neat freak shiny keyboards will keep you quite busy with polishing cloths. Black likes to expose dirt and key shine, too.

Features - Most keyboards are pretty utilitarian devices with little extra features. Gaming Keyboards can get crammed with lots of things. Backlit keys are going to raise your cost but if you need them you need them. Media keys (for controlling sound/playback) and Macro keys can be recreated using software such as AutoHotkey but good gaming software makes it easy. USB hubs are convenient but watch out, they often don't have enough power to run 100% reliably. Whatever you do be skeptical of Gaming Keyboard marketing claims - "Gold USB Connectors Reduce Latency!" is a classic example of this.

And of course price.