This is what I would normally do, or did back when I was learning.
For starters if you haven't already, turn all of the assists off (ABS is fine to leave on), traction control will obviously act completely against getting the wheels spinning and the stability control will try and keep you going in a straight line, it can feel like you are bottoming out in the corners. Manual gears are the best too as you you'll be wanting to have the most control over which gear you should be in at any given time.
Next is to get your car setup, some are better than others to learn with but I wouldn't focus on anything with tonnes of power. Stick with the lower grip tyres and change to AWD as it's the best option if you struggle to hold the drifts. I would argue that you don't need bucket loads of power in the car with the right setup. You only need more power/better tyres once you comfortable at low speeds and want to start zooming around the map at higher speeds, a little saloon car or silvia with up to 500bhp is more than enough.
The drift suspension is usually set up pretty well as standard so add that if you don't want to worry about changing settings, but I'd be looking to change the diff settings so that you have at least an 80:20 or 90:10 split towards the rear, with the acceleration setting maxed at 100% on the rear. If you have closer to a 50:50 split you'll find the car will feel a lot more lumbersome, being slower to get the back end out with more shallow angles, usually meaning you run wide or try to overcompensate and mess the corners up. Having acceleration to 100% allows the wheels to spin up as much as they like making things easier.
I'd then give the car a quick go and see how it feels. Best way is to start a race/time trial/rival on a shorter circuit, somewhere that you can keep repeating the same pieces of road on loop and get an understanding of how to set up and transition between corners. You want to approach a corner in a slightly higher gear, flick the back end out and hit the power. Get the car sliding and then slowly balance your throttle and steering until the car is in a steady drift with what feels like a constant angle. Try and use as much of the road as possible, gently releasing the throttle, flicking the car in the opposite direction and gently re-applying the throttle as you move into the next corner. You'll know when you are in the sweet spot as you'll be able to control the angle of the drift using the throttle, e.g. if the turn is getting gradually tighter then you can slightly increase the throttle to kick the back end out a little more, increasing the rate at which you turn.
You want the car to be hitting high revs, but not bouncing of the limiter. If you are hitting the limiter then try a higher gear as you will slow down and lose the drift, like wise if you are in too high a gear you could simply spin out. It's sometimes worth changing your gear ratios as you'll never be going for top speed and you want the flexibility to be ale to change up or down and hit that sweet spot depending on the corner you're going through.
Rinse and repeat until you have a good feel for the car and can reliably tackle the full circuit, then hit the open world and play about and you'll find things much more manageable. Using a RWD the technique is largely the same, you just have to be a lot more precise and have the understanding of how to control things using the throttle. It's actually very beneficial to get that experience as it will transfer to when you are racing, you will find the RWD monster cars far easier to tame and see the handling benefits over using AWD on everything.
