How to Get A 5-Star Wanted Rating
To get up to a 5-Star Wanted Rating, you'll have to commit lots of crimes. Start with a low 1 to 2 stars by running down or shooting pedestrians or police on the sides of the street. Oftentimes, a mission will put you at a medium to low Wanted Rating by default because you are a criminal, and many of the game's missions will already have you completing crimes.
From a low Wanted Rating, you will have to start fighting back hard against the police resistance instead of merely trying to escape.
How to Escape a 5-Star Wanted Rating
To escape a 5-Star Wanted Rating is very tricky. Don't try to fight back. Instead, just hop into a fast car, a helicopter, or preferably a jet, and vacate the premises as quickly as possible.