How can you tell how to trim your clematis? Are there different types?

I have two Clematis. I don't trim mine at all. I cut them back in the late fall.

Yes, there are different types. Many have 4" to 6" diameter flowers of many colors, but some have flowers only a couple inches in diameter In white that bloom later toward Late summer or fall. Also, some like more sun, others more shade. Most all like rich, soil with lots of rich humus and low growing plants or thick mulch to keep roots cool in summer heat. As for pruning, I believe that is best done in fall to late winter/early spring, when foliage is mostly gone, before new growth starts. You will be trimming where buds for flowers next season are, so expect fewer blooms. I rarely pruned mine unless necessary, allowing new growth to climb up old growth, otherwise it seemed to take forever for new growth to grow up and flower. Many seemingly "dead" vines sent out new runners that bloomed after the first flush of flowers. When I trimmed, I only got one flush of blooms much later.

I have never trimmed mine, and they are always beautiful. There are so many types of clematis, colors, sizes, each one more beautiful than the next. Lydia answered that question quite well.

One of mine has spent years taking over the entire side of the garden that it is growing and all I do each year is take hand fills of it and pull with all my might and rip off new and old growth. I continue to do this until things seem to be back into a manageable amount of growth. I know it will survive and back out of control in no time. I can fill a wheelie bin in minutes. I found it doesn't break down in the compost that well. The other plant I have seems to have suffered because of the excessive growth of the other so I am very careful when working in this area so that I do not reduce the growth further. Both has survived and put on an amazing display.