Nothing. Depending which ones you have, some need pruning, but not now.

A member Spitzhenry did an excellent blog on pruning clematis on June 5th 2009. To find it

Click on 'C' in the A-Z at the foot of this page.
Click on Clematis Plants
Scroll down until you find something by Spitzhenry
Click on her name
That will take you to her Page.
Click on the Blogs section on her page
A list of years and months will appear on the right side. Scroll down to 2009
Then June
Then scroll down to find 'Clematis Prune or Not'
It sounds like a lot of work to get there but it is very quick. If you want to refer to it again in future you can save it in your favourites on your page by clicking on the box provided.