Generally you learn the tracks over multiple games so Monaco on a F1 game will be very similar to a mod for rFactor etc. It's also trial and error and once you are used to it, it will probably only take 3-5 laps to get the general jist of where to brake and such then another god knows how many laps trying to eek out the best lap times
You can also apply your knowledge of other corners to new tracks so you get used to understanding where the apexes are and how slow you need to be going to take certain corners.
My top tip, take it slow, brake early, learn the apex speed then build on that trying to out break yourself lap after lap. Also learn the car/setup as you might get away with taking more curb, breaking while turning or other such driving nuances.
Also practice