Sometimes, holding a pencil is just too much for a little one. Crayons and markers are nice alternatives, but if a child is just not there yet with fine motor development, then you may need to think more creatively.
Children can learn to "draw" in many ways that bypass the fine motor requirements of grasping a writing instrument. On a hot day, they can "paint" with water and sponges on a concrete driveway or sidewalk. The letters don't last long, allowing for repeated fun in the same place. Or try this alternative--shaving cream on a place mat. In this case, I formed the letter in the shaving cream first, my daughter traced it a couple of times, then "erased" my letter and formed the letter on her own. We had a blast!
We've done the same thing with shapes as well. I like it because it gets the placemats nice and clean. You could easily do the same thing on the walls in the bathroom during bath time. What else might be fun? Whipped cream? Pudding? I'd love to hear more suggestions for ways to "write" without writing. Enjoy!