Depends on everything from the field and runway, to the traffic in the circuit, to the aircraft and the pilot's preferences.
In the Super Cub, my prefered approach, noise-abatement permitting, was a very tight circuit, cutting the power completely and putting in full flaps when, or before, abeam the numbers on downwind for a 1000' circuit, or later for a lower circuit. Then I'd turn final fairly close at just a couple of hundred feet.
Compare this to the Europa, which is not a particularly good aircraft for side-slipping. Beacuse of this, I prefer to approach slightly flatter with just a bit of power, which gives me the option of reducing power if I find myself too high (as opposed to slipping which I would do in the Cub). This is particularly important on a short field, but I might approach power-off instead if the approach is over a built-up area to ensure I can make the field if the engine quits. I also prefer to turn final slightly further out (and therefore higher) because I have a couple of checks to do on final (prop pitch set for go-around, gear down and locked).
Then there's the Aztec, an aircraft which I never really got to grips with in the 5 hours I spent flying it. But one thing I did learn is that if I turned final too early or too high I was screwed - its weight and momentum meant I needed a much more stable approach than I'm used to in the aircraft I usually fly.
Very often a published noise-abatement circuit will ruin all the best plans. There's no way you can do a Cub-style short final approach if there's a noise-sensitive village just inside base leg that you have to fly around.
As for traffic, well, all bets are off. Hopefully you can judge your circuit speed early on in the circuit to be able to turn final where you want to. At ATC fields, though, with some traffic joining straight-in, you probably won't be able to plan until ATC tell you whether you're in front of or behind the straight-in traffic. The chances are you'll be behind them, but if you plan for that and are then cleared number 1, you might have to lose height in a hurry!
There are no rules for this kind of thing - at least not unless you're going to fly airliners. Do whatever seems right at the time - and don't be afraid to admit you got it wrong and go around for another try if necessary!
Good luck, and have fun!
FFF
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