There should be NO mail in ballots.. Except in very specific circumstances (e.g. deployed mil.)
Vote on election day only. In person only. Picture ID to vote.
Use (US census) data to eliminate dead people from voting rolls automatically.
Make election day a state/ natl holiday.
Have it so no more then 100 people per voting station. That would help doctors, nurses, and police, firefighters and grocery store workers who will work national holidays.