Something I do with my kids (and it works REALLY well) is get a peice of paper and a pen.
Ask the child how to spell their name.
As they tell you the letters, you write them on the paper. After you get done writing them, have the child then trace the letters of their name with a marker.
After they are done with that, they write their name under the one you wrote for them. (looking at it for reference)
I did this with my oldest when he was 2 and a half and he learned how to write his name REALLY fast.
Hope it works for you!!