As mentioned above, you will see cars waiting outside your Garage for a variety of services. You can also click on other cars around the game area to see if they require anything that you can provide. The best way to take on jobs, however, is to click a Service Bay in your Garage. Then you will see a list of jobs that you can simply click on to initiate. Be sure to collect from the job promptly to avoid losing customers!
Below is a complete list of all the services that you can perform. You will see how there are some really crazy ones as you level up later on in the game!
List of Jobs:
New Tires - Level 7
Wash N' Wax
Spark Plugs - Level 8
Bullet Proofing - Level 9
Biofuel Upgrade - Level 10
Antenna Ball - Level 14
Smog Check - Level 15
Suspension - Level 16
Neon - Level 17
DVD System - Level 18
Nitrous Install - Level 19
Body Kit Install - Level 20
Monster Truck - Level 23
Car Stereo - Level 25
Jet Engine - Level 30
Before you unlock the better jobs later on, you should try to focus on the Wing or Paint jobs, if you can check the game regularly. If you are only able to check once per day, the Hydraulics job is the one to go for if you want the best XP for your efforts.
Later in the game, focus on the better, long jobs, such as Body Kit, Nitrous, Stereo and Monster Truck. If you collect from these within six minutes of them finishing, you also get a 10% bonus for not keeping the customer waiting.
If a job expires because you were not back in time to collect on it, you can visit Doc's Lab, one of the game's more interesting locations (from Back to the Future). If you purchase a Flux Capacitor, and some Plutonium (available to be gifted), you can travel back in time and save expired jobs.
You can visit locations such as the Junkyard to view cars that need to be restored. These require a Workbay and Worker, as well as items. If you quit the restoration job, you lose the items that you have invested in the project.
There are also other jobs that you can take when clicking on one of your own cars. Each needs you to have hired some Friends as Workers. You can see a list of these below:
You can go on Road Trips once you have some Friends to take with you. These earn you a certain amount of Coins per passenger that you take in your car. Hire a Friend as a Worker to be able to begin your trips.
Use the $4000 cars, (those are the Yaris, Pinto and the Beetle) and send them on trips with as many friends involved as possible to get the best return from Road Trips for the least investment.
You again need a Friend/Worker to be able to take this on. A Car Show involves people voting on your car - so it helps if you have purchased some aesthetic upgrades for it. Once in the Car Show, you can share/tell your Friends to vote for you, increasing your chances of winning.
The best way to win Car Shows easily is to buy cheap cars and then add on as many aesthetic modifications as possible. These include things like high suspension, ridiculous alloys, neons, spoilers and so on. There is no point in adding performance boosts to a Car Show entry, as it will not help you get a good result.
You can use service vehicles or your own car to deliver various items across Car Town in short jobs that earn you a few Coins.