Dr. Rob is right... don't make the mistake of buying a dirt cheap one first. I did and of course regretted it. I replaced it with a Harris and despite the fact that the Harris LOOKS identical to the cheap one, it is not.
I also opted to get one that does not tilt side-to-side... that's just my choice. Most people seem to like the ones that tilt, but I wanted something that would not move once I planted it where I wanted it. So far, I like it. It a good balance of quality/affordability.