The general rule of thumb for pruning is fairly straight forward. This group of Clematis usually require little attention until they are mature and need to be contained. T hose that bloom in the summer fall into two categories. Those which bloom in early summer should have any dead or damaged growth pruned back in early Spring to the first set of healthy, fully developed, strong plump buds. Those which bloom later and into the Fall should be cut back to 1-3' above the ground.
T hat's it.
Not really too intimidating. If you want more detailed information about Clematis the best book is the one by Christopher Lloyd and there is a copy of it at the library.