Interesting thread. Well, it just happens I've been done quite a few PFL's in the past 3 weeks as part of my PPL revalidation (I passed the check!). For what they're worth, here are my thoughts:
1. In this part of the world, many fields are of the tennis court sized variety (definitely not East Anglian sized prairie!) with big stone walls round the boundaries, often with a diagonal or side slope and a hummocky surface as well. This somewhat limits your choice of landing site. I accept that once the aircraft is on the ground, the deceleration is going to be quite rapid on the rough ground, but I would prefer it wasn't caused by a block of granite. So, a search for a reasonably long flattish field is always a good idea. Of course I accept that in a real forced landing you may not have this luxury.
2. Long straight-in glide approaches are hard to get right, even with a slip or S-turns. The "high key, low key" method, with a tight base leg is much better. The aspect of the base leg can be varied to lose height if you are too high, ie too high, then turn away from the field sufficient to lose height. If you are really high, by all means orbit on base leg.
This is invariably the way I practice glide approaches when landing at my home airfield, and it works every time.
3. By all means slip the a/c to lose height on final, but be careful with the flap limiting speed. On one PFL I had flap 40 selected on a C172, tried a quite aggresive slip and quickly found the speed was 10 kts above the flap limiting speed -quickly corrected before the instructor noticed! In fact accurate speed control is vital to the exercise - try diving for the field in this part of the world and you will end up building up excess speed and probably going into the stone wall at the far end.
4. Most engine failures are caused by carb.heat or fuel problems so your first actions after pitching for best glide speed should always be to pull the carb heat knob and check/switch the fuel selector, and switch on the electric fuel pump if one is fitted. Fly the aircraft right down to the ground, send a mayday and don't bother with the transponder.
5. In most of my practice PFL's, being too high was far more common than being too low.
6. Try and pick a field that roughly aligns with the into-wind direction. Be aware of the wind strength and direction at all times, especially when turning from base onto final.