They should fit well in your hands. If they are too large or too small, they will not be very comfortable to work with.
Try to get a pair with a spring in the handle (like the pair pictured). The spring will save your hands from extra work.
Look for a pair with a nicely tappered nose. Sometimes I've seen low-end (as in cheapo) round-nosed pliers with a nose that's very thick in diameter. This means you can't make small loops when you need too, and they are generally bulky and not very comfortable to use.


