It really depends on what racinggames you want to play.
Hardcore simulators like Assetto Corsa, simcade simulators like Grid or some of the Need For Speed games or all out arcade racers like the Burnout series.

I'm not going to pretend I'm any good at racing because I probably aren't but I had the most useful learning experience from the drivingschool in Richard Burns Rally. Which is the only game I can think of that actually gave some useful tips about weightshifting and how to take corners while using the brakes to get more grip on the front tires so you can steer more easily.

As for car setups that is a tough one, it's really technical and I can't think of a game that gives good suggestions. Most information they give for setting the suspension of a car for example, while correct most of the time, only serves as more confusion if you're not already familiar with it, so is pretty useless. Best is to go online and look for information on the internet, but also this is not always reliable and sometimes games live by their own rules, especially older titles.
Often using extreme settings and trying it out will hint what it does but it still requires an amount of tinkering to get a well balanced setup.
What I would really like to see in a racinggame is some sort of setupadvisor that gives helpful suggestions (come to think of it I think some of the Codemasters F1 games have this but I'm not sure).

Another thing that is important is what control method you use, a steering wheel or a gamepad are the most common used.
I use a gamepad but it does mean I can't play certain games on some consoles for example, games that require rightstick throttle and brake are unplayable for me, which means most racinggames on the Playstation 2 and 3. I have less problems with the Xbox gamepad which uses the triggers as throttle and brake. While I have a steeringwheel somewhere in the storage, I do not have a good seating solution to accomodate it and when I use it I only get backpain because of it, so I'm not using it.
But when you do make sure the steering behaves like you want it and adjust settings if needed, steering must be intuitive, not too sensitive and not to sloppy.

So what tips can I give?
Racing is managing your speed, if you have a high power car it mostly means you're using the throttle conservatively and using too much throttle will only end in overshooting the racingline.
Try using the brakes to assist in taking corners if needed.
A lot of racinggames have crap A.I. like the first Forza game on the Xbox for example, really avoid this game and move on to the later ones as they're all much better.

Well, that was useful.

I usually play mostly arcade, but the goal is to play better on more realistic games (rFactor and so on). I'm interested on Richard Burns Rally... does it have a virtual instructor or the tips are only written on the manual? I liked the flight school on Flight Simulator because the instructor told you in real time how to do things, and warned when you were doing things wrong. I have not much space to spare, so I think that I'll use a Xbox One gamepad instead of racing wheel.

I'm more interested in racing than in engineering. When I talked about 2CV (and the Reliant Robin) I was thinking on extreme cars that push simulation to the limit (yes, a car that barely makes 110 kph / 65 mph), not about settings as in F1 simulators. The 2CV is a strange case because the suspension springs behaves opposite to any other car in the world, and the Robin... well, it seems that AI can't understand that its very hard to control the weightshifting to the front wheels when there are no wheel to receive that weight. It makes me curious about how this games are programmed.

Zup wrote:

Well, that was useful.

I usually play mostly arcade, but the goal is to play better on more realistic games (rFactor and so on). I'm interested on Richard Burns Rally... does it have a virtual instructor or the tips are only written on the manual? I liked the flight school on Flight Simulator because the instructor told you in real time how to do things, and warned when you were doing things wrong. I have not much space to spare, so I think that I'll use a Xbox One gamepad instead of racing wheel.

I'm more interested in racing than in engineering. When I talked about 2CV (and the Reliant Robin) I was thinking on extreme cars that push simulation to the limit (yes, a car that barely makes 110 kph / 65 mph), not about settings as in F1 simulators. The 2CV is a strange case because the suspension springs behaves opposite to any other car in the world, and the Robin... well, it seems that AI can't understand that its very hard to control the weightshifting to the front wheels when there are no wheel to receive that weight. It makes me curious about how this games are programmed.

Richard Burns Rally driving school has him as codriver but I don't think it's worth it to get the game for that as the driving school is maybe 5 short lessons or so, it's just that it was the most enlightening of driving schools as most just require you to accomplish things in a certain time.
If you want to get anywhere with games like rFactor you really do have to spend time on setups. In GTR 2 for example (rFactor engine) you could only get gold gears after tinkering with the car.

A quick update:

I've checked through most racing games on my collection, and I've found that GTR2 (Simbin) has some driving lessons. It does not have a copilot, the lessons are "watch and repeat"... but at least I can learn something.