Why don't you capitalize the first letter of your sentences and put a period at the end of it unless it ends in an appropriate exclamation or question mark?
that's actually not quite what i do. i quite often skip question marks also, and i usually do use periods, unless it's the last sentence, because at that point it is obviously the end and a period in that case would be unnecessary. but the reason i usually don't feel the need for capital letters at the beginning of sentences is actually because i DO use a period, at the end of the previous sentence. i hope that makes sense