First, be careful with microphones that do not list certain specifications at all. Most of the time, if a microphone isn't accompanied with certain specifications, there is an obvious reason for it.
Have a look at sensitivity, a microphone that is not sensitive enough can get you into having to turn up the volume of your pre-amplifier to such a level that it introduces noise. Secondly, check the frequency range. For vocal recordings, you should be good with most of the microphones, but some really cheap mics do miss a lot of low frequencies.
Decide whether you wish to buy a condensor microphone or a dynamic microphone. While both can result in pretty good sound on vocal, a condensor microphone gets the transients better since its membrane is lighter (in weight), which means a plus to the intelligibility of the words. Drawback however is that a condensor mic normally should be used in conjunction with a pre-amplifier that has +48v phantom power.
Also, take a look at the "self noise" levels, some are significantly higher than others.