Just use a little less dextrose at bottling time. Some of the software programs will allow you to calculate how much dextrose to use to achieve a desired carbonation level. Best to weigh your dextrose rather than using a measuring cup.
What I've always done is adjust the amount of priming sugar based on the type of beer. For example, my brown ale is overcarbed (ask Mutiltated!) but I used the amount of priming sugar I always do (4 ounces per 5 gallons). If I make a brown ale again, I'll reduce the priming sugar. If you have brewing software (I have Beersmith), this is easy to do. Or you can use a carbonation chart.
The next time I make that brown ale, I'll use 2.75 ounces priming sugar, per Beersmith.
Here is my dumbed down version of why overcarbonation happens according to what I understand and have learned from reading the topics here... I'm hardly an expert or anything but... overcarbonation may happen as a result of any of the following:
1. You don't wait till fermentation is done before you bottle, so there is still unfermented sugars in your beer which makes for more sugar for the yeasties to eat, thus more carbonation
2. You put too much priming sugar
3. I seem to remember reading some comments about not enough headspace in the bottles, or maybe it was too much headspace ??? Anyway, I'm not sure if thats true or not but I think some people have that idea just based on what I've read.