Give the child a square to write in...have them practice their letters by touching top of the box, corners, sides. This builds an understanding of the spatial relationships. Also, there are many great printables out there for fun practice that have circles, waves, and zig zags. Try mixing it up a bit and add in some cutting skills--all prompt fine motor skills. I would strongly suggest investing in some play dough --even cooler if you find a recipe off pinterest and make it together--and "build" the letters with play dough snakes. My kindergartners LOOOOVE this activity, we did lines, circles, then moved to letters, and by the end of the year first names and sight words.
Another tip is to make your own 3 line paper, top line is blue for the sky, tall letters touch the sky, red fence, bottom line is green for the grass...this is part of handwriting without tears--just google it and there will be tons of info. Use what works for you...some of it is great stuff
I personally love this website: http://www.handwritingworksheets.com/
I make practice writing sheets for each child using their first names, targeted sight words, and eventually first and last names.
Another tip, try having your child "correct" their paper. Give them a cool pen or highlighter and compare their letters to the "real" letter and circle the one they feel is best. Let them give themself a sticker and hang the paper up on the fridge. My little ones would run at me with their papers to show me how perfect their letters were.
I hope some of this helps!