Lots of good advice here. I’ll add a few things that helped me get better.
For me, the first thing I did to finally start improving was to … slow down. When I first started playing Forza I would drive way too fast and always end up off the road or crashing or losing traction and rewinding. I was too focused on trying to gain the lead at the start of the race. This is a really bad way to play especially if you want to compete in multiplayer.
Which brings us to the first thing: turn off rewind. This is probably the most important thing you can do to get better. Driving fast is about being consistent. If you are rewinding a lot it means you aren’t being consistent. If you find you are driving off the track or losing control, slow down, brake earlier.
Turn up the drivatar difficulty. At the lower difficulties the AI is just too slow to race against. They are so slow that it will affect your own driving because you’ll be trying to avoid their unrealistic behavior. I would say set it to at least above average or expert. Don’t worry about getting first, or even on the podium. Just finish the race clean, and at least hold your position. Before you know it you’ll be cleanly overtaking and moving up in the races. Once you start to podium, bump up the AI one notch.
Start with lower division cars. Sure driving the F1 and prototype cars is fun, but as a new racer those cars are going to be beyond your ability. Start with something easier to manage, something in class c or b maybe. The modern hot-hatch ghost MP lobby is a good place to start, so learn to dive the cars in that division against AI. Learn to beat the AI in the lower class cars, then move up to the high end race cars.
The hardest thing for me to learn was braking. A lot of this comes down to familiarity with the tracks, and each individual car. I just did a modern SUV league event the other day, and felt like I had to completely re-learn braking; oh my those things are heavy. If you aren’t familiar with a track, don’t try to overtake on the first lap. Instead, try to drive close behind the car in front of you and watch their tail lights: as soon as they start braking, you do too. The AI knows the correct braking zones, so you can learn from them. After you get comfortable, then you can start to push the braking zone to try for an overtake. The AI has corners that it is strong on, and corners where it is weak. Racing is about identifying those weaknesses and using it to overtake. As an example, at laguna seca the AI is terrible at turn 6. (http://www.onehotlap.com/2013/08/map-of-laguna-seca-with-track-geometry.html). Try to overtake them on the straight uphill coming out of turn 6; just be ready for the corkscrew.
I found that turning off the suggested line/braking line helped me improve. The braking zone is going to be different for every car, so it requires being familiar with the track and the capability of the car. I feel like the suggested line actually prevented me from learning either.
That’s my advice. And while I’m not great at the game, I am able to beat unbeatable AI on the longer race lengths. Just have patience, and above all else: drive clean.
Oh, and watch this video, lots of good real-world advice:
Lime Rock is one of the tracks in the game, so you can go see exactly what they are talking about in that video. The Lime Rock track also has cones placed a the turn-in, apex and track-out points, so it is a very nice track to learn to get faster on. Other courses (I’m looking at you Silverstone) can be harder to learn because there aren’t as many reference points.