I see that I have spoken out of turn. I did not realize there was a lack of training in this area of slips and cross-control stalls.
In my country, training and demonstrated proficiency in these maneuvers are required of PPL's and especially FI's.
But, having let the cat out of the bag, I feel I must explain my comments with a little more detail.
Let's take Classic's comment as an example. He says slipping is a bit like taking your car out of gear and coasting. Exactly! That is the idea. Imagine that, for some reason, perhaps to sneak in quietly, you want to do exactly that: cut off your engine and coast quietly into a spot. You must arrive exactly at that spot. If you cut the engine too soon, you will stop short. If you cut the engine too late, you will overshoot and have to apply your squealy brakes, announcing your arrival. So, you have to cut the engine at precisely the exact right moment. This is very hard to do. And the weight and speed would always have to be the same. But what if you can apply a little bit of braking without too much noise? then you can delay the engine cut a few moments, knowing you will arrive with a little overshoot which you can kill with a little braking. Wouldn't you do that? And the only variable in the car is speed and weight, but in the airplane, the big, big variable is wind. Wind will certainly change as certainly as your girlfriend's mind will change with not a whit of notice.
So, no matter how skilled you are at judgeing your "key" position, if you arrive there on speed and on altitude, there will come a day when you will still fall short of your spot, because the headwind will increase and push you back.
So, it is a good idea to always arrive at your "key" position with a little extra altitude and plan on "slipping" it off. Slipping instead of flaps at that point, because flaps cannot be retracted if you misjudge, but a slip can be immediately stopped if you think you are dropping short. Then when the field is assured, use flaps.
So, besides the plain, simple, long-established fact that slipping is a good idea, it is a required maneuver for a PPL license.
Practicing cross-control stalls is how we get used to the feel and sight and handling characteristics of a particular airplane so that we don't accidently stall it when slipping. Older airplanes sometimes did not have flaps, and slipping was the only way to lose altitude without increasing speed. Standard procedure.
If you have not been trained in slips and cross-control stalls, well, of course you should get a feel for it with an experienced instructor.