Handwriting is a very complex task and requires many foundational skills to be developed before your child is ready to begin handwriting.
Two of these skills are hand-eye coordination with pencil control and intrinsic muscle strength (all those little muscles in the hand).
A great activity for encouraging the development of these skills is colouring in. As your child becomes more motivated to stay in the lines they improve their pencil control and strengthen those little muscles at the same time. Colouring in often gets a bad rap but in conjunction with free drawing can be very beneficial.
Colouring is also very therapeutic and fun for adults! Thanks to Little Gnome, where I got my adult colouring in book today! (In pic).
Check out pinterest for some nice simple colouring in for your children to start with and then as their control improves decrease the colouring space.