You must know what fruiting habit your berries are.  Some fruit on current season wood, others fruit on last years wood.  The ones below fruit on last years wood.  Some even fruit on both.  Which means you can get two crops, spring/summer and fall.  These can be mowed down with a standard mower in the spring and gain a very strong crop in the fall only.

The above image are unpruned raspberries.

Pruned by simply removing the dead canes.  

More information can be found at The Ohio State University.