Most important rule is always remember to service the car after the last race of the stage. Because you won't have access to the loaner car in your garage before next stage starts. 

 

Going along with servicing, any upgrades should be done immediately when you start the event. But assuming it's not 24+ hours required to deliver, park your car before you start the final goal of current stage. This way you can start next level of upgrades before completing the stage. 

 

Edit added April 21 - Looks like the Monkey's are now limiting us to one stage of upgrades per day. 

 

Not always required, but take advantage of your agents during the event. One can usually do the entire stage in a single racing session if you don't have to wait for repairs. 

Edit June 2 - In regards to increase cost for agents in version 3.4.  Instead of playing the 5 gold for a higher class car, go back to career mode in the Amateur class and hire the agents there.  When you go back to the special challenge, they will be selected and available for use.
 

This being said, if your car is in the red for servicing, try the next goal to see if you can still finish it with a car needing service. You'll be surprised how often you can still complete the goal. 

 

If you find yourself needing several attempts to complete a goal and your car gets into the red, take advantage of cloud saves. If you can't complete the goal, reload from your last cloud save. If you get into habit to make a cloud save after each completed goal, you won't have unnecessary servicing. 

 

Events usually start when the update is released and end with an extra day at the end to account for different timezones. Stages unlock at midnight local time. So it's possible for some parts of the world to complete the first two stages in a few hours after update is released. If there are multiple challenges in an update, those events will open at midnight UTC.  Even though event is available as mentioned above, the event doesn't officially start counting down until you start the event on your device. So choose time to start and end event based to what is most convenient to your schedule. 

 

Should you find you don't have time to complete a stage one day, you can still catch up and finish it the day after along with that days stage. If you really wanted to, start the event and park the car. Wait until the last day and do all the stages in a marathon session. 

 

For time trial goals, don't always set the best time. Occasionally future goals is to beat your last time. 

 

Goals for some races don't have you finishing first. If you want to maintain all golds in your achievements, finish the race in first. You'll get the Failed completion banner. Retry the race to complete the goal as described to advance to next goal. 

 

The remaining tips are definitely not items that Fire Monkeys will endorse. So use at your own risk. 

 

If you want to start a stage earlier that midnight your local time, you can change the time on your device. Change the time zone to something east of your location. Usually either UTC +12 or UTC -1 depending on when event started. Yes you can attempt to go even further ahead and change the date also, but it's hit and miss in that some stages won't open until a hotfix from FM servers is applied to open that stage independent of local date/time set on your device. 

 

To avoid servicing, disable Internet access to your device. Advance date and time on your device appropriate number of hours needed for repair. Switch back to RR3 to ensure repair complete. Restore proper date and time. Note, if this is done, there is a high probability that at the end of the event, you won't get the rewarded car at the end. You'll get a cryptic message about gametext and it won't show the car as a reward on the stage selection screen. 

 

Edit April 21 - The below is no longer applicable in version 3.3

 

Other option to avoid servicing is to use the engineer. Hire the engineer for the race. But service level is only maintained if you finish first in the race. But you can get around this by force closing the game. Do this immediately after you get the green Complete banner and you'll maintain service levels and keep the agent. Note, by doing this, you usually won't get any R$ and fame rewards since you're force closing the game before the rewards are given. Occasionally you'll get a large lump sum of missing backlog of rewards when you restart the game, but it's hit and miss. 

 

To start a new stage, the game requires an Internet connection. But if you wish to race the offline bots, once you open the stage and get to the first goal screen, you can go offline for the remainder of the stage. 

 

Feel free to add additional hints and tips or corrections to the things I've listed.