Make sure you eat lots of carbs before your match
. The bounce on clay is pretty high so it takes a while to get used to. You have to be patient on clay and work the points much more. If you start going for winners early you will find yourself racking up unforced errors.
Try and work different tactics to pull them wide out of the court and then hit in the open space. Try to practise slice and topspin angles.
Good luck, clays a nice surface.