If you are asking about how to stop your bike in as quick as time as possible, then in dry conditions the front brake is all you need. Make sure it is working properly and that you have good pads and a short pull distance.
As pointed out though, in low friction conditions such as wet / ice / gravel etc. then it can be useful to have both brakes (if you have them) operating. I'm not sure whether you would ever apply the front brake and skid the rear at the same time - I certainly don't. In the example of a 4x4 pulling out on you on a dry road, I'd be straight onto my front brake and looking for a way round. Failing that, try not to get under it's wheels ;-)
If you are talking about stopping quickly without a front brake, using only leg braking / skidding, then hockey stopping is a good technique for scrubbing speed quickly. It's basically doing a skid stop but sending the back wheel a bit sideways. You get more friction that way, as the tyre is sliding sideways along the road, rather than in a straight line. I think the tyre / rim then act a bit like an edge of a ski does, when stopping.
And, if you are talking about skidding for fun / showing off, then balls over the stem is the way to go. Obviously, the more you unweight the rear wheel, the less actual braking you will be doing.
If you are asking about how to stop your bike in as quick as time as possible, then in dry conditions the front brake is all you need. Make sure it is working properly and that you have good pads and a short pull distance.
As pointed out though, in low friction conditions such as wet / ice / gravel etc. then it can be useful to have both brakes (if you have them) operating. I'm not sure whether you would ever apply the front brake and skid the rear at the same time - I certainly don't. In the example of a 4x4 pulling out on you on a dry road, I'd be straight onto my front brake and looking for a way round. Failing that, try not to get under it's wheels ;-)
If you are talking about stopping quickly without a front brake, using only leg braking / skidding, then hockey stopping is a good technique for scrubbing speed quickly. It's basically doing a skid stop but sending the back wheel a bit sideways. You get more friction that way, as the tyre is sliding sideways along the road, rather than in a straight line. I think the tyre / rim then act a bit like an edge of a ski does, when stopping.
And, if you are talking about skidding for fun / showing off, then balls over the stem is the way to go. Obviously, the more you unweight the rear wheel, the less actual braking you will be doing.
Anyway, hope this helps. Stay safe.