Keep your hands dry! First, be sure to wear liners that wick moisture away from your hands and have an extra pair on hand for mid-day changes. Second, thoroughly dry the inside of your gloves by wadding up newspaper and placing it inside the glove to absorb the moisture. Fully open your gloves when drying.
Consider activity levels when deciding the proper insulation/comfort rating. If you're driving a tow motor, a higher level of insulation will be required to keep hands warm and safe. More active jobs require a lower insulation level. Also, if you have circulation problems, consider a higher level of insulation for increased safety.
Gloves should not fit too tight. To provide proper insulation, some air space is needed between the hand and lining of the glove. When sizing gloves, try them on at the end of the day when your hand is a bit larger from swelling.