I came up with an easy way to help young writers remember to start each sentence with a capital letter and to use punctuation at the end. During their writing time they can make noise. They may beep when they put a period and then clap their hands above their heads to remind themselves to make the next letter a capital. At first everyone did it and it was fun but it also worked! Now the ones who are continuing to do this don't even bother the others. It's become a normal part of our day.