• who is using your scale? I recommend a scale that has “athlete” mode so that you can use the scale to measure all members of  your household
• similarly, if you want to use this as a body fat percentage calculator for kids, see if the scale has a children mode
• see whether the scale can remember dimensions and scores. For example, does it remember height and gender for different people?
• quality matters – the longer you can consistently use the same scale, it will be easier to measure your progress

When actually using the scale, remember to stay hydrated and weigh at the same time each day. If you are exercising before measurement, make sure you are still hydrated. It would be best to simply weigh yourself at least 1/2 hour after drinking a glass of water. If you have access to a body fat percentage calculator caliper, you can also use that as a relative measure in conjunction with the body fat scale.