The one thing everyone agrees on is that bedwetting is not an emotional disturbance or willful misbehavior. Behavioral modification techniques do tend to help, though, usually in conjuction with other approaches. Eventually, the problem does almost always resolve. However, as they say, eventually can be a long time. This approach relies on a sort of subconcious programming by suggestion before bedtime.
Techniques involve stories, record keeping with star charts and so forth, and lots of encouragement.
Having said that, it is quite cheap and in actual use over many years has had very few adverse events. I do use it myself for some cases. This is used as a nasal spray or now an oral preparation at bedtime and tells the kidneys to drastically reduce the amount of urine produced. Bladder capacity exercises. If nothing else, it does increase the child's daytime awareness of the urge to void and maybe helps at night.