My DS just finished a mid-year skip to 2nd and struggled with handwriting. It's now much much better but not fantastic. His teacher just had him write and write and write. She is big on storywriting and would give the kids a prompt and turn them loose with requirements. The repetition helped the most.
We also did a lot of hand work with therapeutic clay and small bead work. I also taught him how to make bread by hand (he loves to cook) and he did a lot of kneading! It helped him hone his skills and strengthen his hand muscles so that he wouldn't complain of being too tired or get cramps.
If you google occupational therapy and handwriting, you'll get a lot of good suggestions. It can all be fun without a therapy feel to it!
