If you have done a great drawing or taken a really nice photograph that you would love to paint in watercolor but the drawing or photo is the wrong size or you you can't draw without erasing all the time or you just plain old cannot draw. Don't let that stop you from painting it in watercolor. Take your drawing or photograph to a photocopier and enlarge it to the size you would like to paint it. Or if you have a scanner, scan it and resize it to the size you want to paint it. Take your copy or print out and tape it to a window on a sunny day, then tape your watercolor paper over top of it. Now you have an instant light table. The sun will shine through both papers and you will be able to trace the image onto your watercolor paper. Use an HB or No. 2 Pencil (same thing) and lightly trace, try to use as few lines as possible and try not to erase too much!
You can paint in watercolor even if you can't draw ... you can trace! It's okay.