1. Your choice of a voice recorder will depend on where you will use it, and how long your recording time will be.
2. Determine whether you need a recorder that will give you high quality in terms of sound, or whether a low quality recorder is acceptable.
3. In some cases, you might need a separate microphone aside from the built-in microphone that the recorder has.
4. If you need to use your recorder frequently and you are not able to transcribe everything before the next recording, you will need one that has the capability to transfer files to a computer. 
5. Choose a voice recorder that does not have too many complicated control buttons.
6. Other considerations in choosing a voice recorder are the kind of batteries needed, if it can be plugged to an electric outlet, and whether its memory is expandable.

via howtodothings