^^^ I saw that one, and it's good stuff. Wondering if anyone else has any other perspective. This kind of thing is all about feel, which is tough to write out.
Merun's notes are basically on point here, but since I struggled for a long time with drifting I'll drop a few pointers.
If you're dealing with drift challenges -- and these are of course the hardest -- you need to get a feel for the car, and *when* it actually starts drifting. Don't be afraid to just go full blast through a drift zone. You'll probably go off the rails -- that's fine, it's not always apparent if the car you are driving will handle the drift like a champ or just go flying (supercars *will* go flying). Once you see what fails, you can start figuring out what works, and so...
If you are having trouble initiating the actual drift (believe it or not, this was my biggest problem), what *should* do the trick is, when you have enough speed, hit O (handbrake), and then tug all the way to the direction on the left stick (left or right depending on the direction, obviously), but do *not* continue holding the stick. The car should already be in its drift state, and from there, things get even trickier.
You want your car to go as sideways as possible *and* be going as fast as possible. You can do like 10 runs on a stage and get drastically different scores even though things *look* the same -- this is because, I think, the game really does care a great deal about speed and angle of the car as you go through a drift zone. Obviously, this is easier said than done! Once you are drifting, figuring out just how steep the car angle can be before you invariably lose control is a balancing act that seems more determined by the car than your ability behind the wheel. Don't be surprised when it takes many runs to even get a feel for how far you can push it and at what speeds.
More importantly, you really need to understand the track. The drift tracks are designed in such a way that's not always apparent where you should actually begin drifting, but there are enough hints (mainly in the curvature of the road itself) to get you started on seeing how you should drift. This tells you nothing about a very important aspect though -- your angle of approach into the drift.
The truth is, it's not just angle, but actually spatially where you are on the road -- sometimes coming into the drift from the middle will be best, other times left, and other times right. The trick to figuring out what is best, past just throwing shit at the wall and seeing what sticks, is to figure out what angle and position gives you the most throughput on the drift -- ie. maximizing how much time spent drifting. Again, speed and angle seem to be a factor of score once you actually get into the drift. Sorry to say, this is really up to you to figure out, since there's just too many variables to give a firm answer on 'what's best'
The other thing to be aware of, at least when dealing with the drift challenges, is that the speed sections are absolutely crucial in 3-staring the track. It is much, much better to optimize those speed sections than having that "perfect" drift in my experience. If you have to make a decision between maximizing drift score, and entering a speed zone at a snails pace (because the recovery time is very poor on some cars), always prioritize speed. The faster you are going in a speed zone, the more points you get, and it is *much* easier, ostensibly, to get those points than to get a perfect drift going.
In actual races in which you need to drift, I almost *never* use handbrake unless it's part of the requirement to 3-star the track. In these cases I use a hard tug on the brakes and let speed do the rest to knock your car into the drift. Drifting will happen a lot here and there, but only in small increments. You are almost always faster just breaking a bit and gassing around corners, so long as your car isn't fishtailing (which will happen in some fast cars). If you are going fast enough, and hitting a green flag turn, you can probably get a very nice, barely-there drift going which will be faster than letting off the gas.
Choosing cars with a high rating in drifting will help if you absolutely must drift. For all other cases, a faster car with good enough handling (ie, it doesn't fishtail like a mother fucker when you tug hard on the brakes) is probably better for normal tracks that don't require drifting to 3-star.
Hopefully that helps. Because every track and car are different, there is no hard rule to drifting in driveclub. But you'll find if you prioritize using a car in each class (when you can, at least), you will develop a feel for how the car can handle at varying speed, and body memory will definitely kick in.