Earn 100 Gold medals across both factions

You need to earn gold on 100 events as either a cop or a racer. There are 136 events in total so you don't need to gold them all. You'll need to play a lot of events here for the career mode, so during your career mode speedlists, focus on playing events you don't yet have gold on. You can keep track of how many events you've got gold on by looking at "Driver Details" from the All Drive menu. You can only see one faction at a time, so hit to switch between cop and racer.

Some general tips for event types which should help you gold most events on your first try:

• Rapid Response
  Go as fast as you can but it should be a priority to avoid hitting anything. Slowing down around tight corners will save you more time than ramming into the walls. You get penalized 0.5 seconds for the first collision, 1.0 seconds for the second collision, 1.5 seconds for the third and so on. That's a 1.5 second penalty ON TOP of the previous penalties of 0.5 and 1.0 seconds. So it's in your best interest to not hit anything. You will have plenty of time to make it to the finish in time for gold if you avoid hitting anything. You can probably afford a collision or two but try to avoid them altogether.
  
  
• Interceptor
  EMP the target right away and then ram into them using your ESF. Wait for them to start running away and then repeat once more. You can take guys down in 30-60 seconds nearly every time with this method, even the Hard events.
  
  
• Hot Pursuit
  My strategy was to EMP as soon as the event started, and turn on ESF for whoever I could hit first. Then focus on EMP and ESF the guy in first place. When he gets hit, he'll fall back and someone else moves up to first place. I'd do the same to him. Make sure to use repair shops on the way to replenish your weaponry and health. By the time you get to within a few miles of the finish, everyone will either be taken down already or nearly dead, so a few rams and weapon hits will finish them off.

• Race
  As a racer, I preferred to have ESF and Shockwave equipped. I'd try and shockwave 2 or 3 cars at once and use ESF on another right away. Then I tried to stay in front the whole time and saved my ESF to counter against EMP attacks, and used shockwave when I saw someone coming fast behind in the rearview since the shock will send them backward and slow them down considerably.
  
  
• Hot Pursuit
  Basically the same as a normal race, but now you need to deal with the cops too. For this, making use of the Repair shops is crucial.
  
  
• Interceptor
  You can either escape or take down the cop who starts giving you chase. On the hard missions, you may find it easier to simply take down the cop. Drive forward a few seconds then perform a 180 turn. Ram into the cop with ESF and Shockwave immediately then keep ramming him until your ESF and Shockwave are available for use again then repeat.
  
  
• Time Trial
  These are like the Cop Rapid Response but you don't get penalized for colliding into the wall. But if you use the same strategy and avoid wall hits or hitting other cars, you'll make the times on these with no trouble at all.