Police:

Upon reaching level 4 (Most Wanted) there will be an overwhelming amount of police officers coming after you. At this level, cops are excellent at boxing you in. If you cannot move forward, use reverse for two seconds to get away from the block. Spin your car around and get out of there.

For an easy way to get away from cops at high wanted levels, find the baseball field. Look on the map for a small triangle towards the top left. Use highways in a circle around the field to achieve your missions. Once you have gained enough bounty, city damage, roadblocks, etc., drive through an entrance to the baseball field, hitting the pursuit breaker on the way in. Make sure that you slow down some before hitting the breaker so that it does not send you through the other side of the field. Once you make it in the field, stay there and wait out the cool down period. The cops should be off of you, and cannot find you. This works almost all the time to get rid of the cops. Just driving through random blockers rarely works when you are at wanted levels 4 and 5.

The best way to escape the cops is to evade long enough to get into cool down mode, than find a hiding spot. By sticking to the cities you will find lots of cool down spots to sit and hide your car until the heat is off. This is also a good way to avoid helicopters which appear if your reach level 4 on your map. Another good method is to run into the triangles on your map, which mark places where you can ram into shops and other roadside items to disable the cops. Highways are good places to get blockades and strike strips which are challenges for milestones.

Once you complete Razor's (Blacklist #1) five challenge races, an intermission sequence featuring you, Mia, Razor, and the other Blacklist members will start. Once you get your car back (BMW M3 GTR), you will go to a heat level 6. Every cop in all cities will try to bust you. You must evade them for five minutes, then you will get a call for Mia. Try getting to the golf course. There is a little building that you can crash into to get rid of the cops. Then, try to wait it out until you get Mia's call. An icon will then appear on your map. Quickly get there as soon as possible. Get to the spot, jump the bridge, and you will be home free.

Never respawn your car in a pursuit, as the police will always catch you.