What is a good recommended way to help a child stop bedwetting?

Bedwetting alarms. These have been shown to be very effective in helping stop bedwetting. Other ideas are to lessen the amount of fluid your child drinks before bed, or to have scheduled awakenings during the night and take a trip to the bathroom. Talk to your pediatrician to make sure there is not a medical condition causing the bedwetting.
Loving support. Don't blame the child. Withhold fluids after supper, toilet 1 - 2 hours after child retires. Older children should take care of their own sheets/bed clothes. Enuresis alarm with necessary parental support if necessary (help to wake, switch off alarm) & has best cure rate. May need medication help with desmopressin (ddavp), long acting bladder muscle relaxants or imipramine. Always be supportive.
Bedwetting Alarm. I agree with dr. Webb's answer, but would add that the alarms are not usually effective younger than 5-6 years old.