ou will be scored on your missions progress and how well you do during your current mission. You can re-do missions so if you make a mistake you can correct it. Try your best at the missions and get to know the missions. Once you know what to do you shouldn't have any issues scoring 100% in each one.
Here are a few things to note:
You cannot die during your mission.
If you die, don't use a taxi during the mission. This will go against your completion and reward you with a 0% rating.
You can only replay missions once you have completed the main story.
The Ballad of Gay Tony Gold Star Achievement Guide