There are a few different tools you can use to trace a pattern onto fabric. I'll list them in order of my personal favorites:
1. Heat-erasable pen - this is the easiest tool to use. easy to trace and easy to erase the lines with heat when you're done stitching.
2. water-soluble marker - this method is the next best option for tracing. Trace your design and rinse your fabric in cold water when you are done. Lay fabric flat to dry.
3. Pencil: If you are absolutely desperate and don't have access to a heat erasable pen or water-soluble marker, you can use a #2 pencil. This will work, but it will be much more difficult to use and harder to erase the lines when you are finished.