In the sidebar, you will find a downloadable PDF of words (A to Z Word Bank) that is a great start. The word bank is perfect for a "Letter of the Week" curriculum.
Print out the word bank and assign one to two words for each day that you child writes onto paper. Consider creating a little lesson around each word. For example, if the word is 'airplane' then consider reading a book on airplanes and making paper airplanes. Not only will you incorporate reading and writing, but you will touch on physics too.
For children who are already writing well, use the words in small sentences that focus on sight words too.
Also, have them draw a picture with the word being in the picture.
Remember, it is important to stay calm while teaching children about writing.