You need to figure out exactly what causes you to be late.
Do you get distracted, on the computer? If so, stay off of the computer, when you need to go somewhere.
Is it last minute "must do" things? Set an alarm clock, for 10-30 minutes before you need to leave. When that alarm sounds, consider it your signal to quickly wrap up any last minute details . . . then LEAVE THE HOUSE. Don't give yourself even a minute, to get distracted again! Try to leave earlier than needed; you never know what traffic will be like.