AOA
Clive, I've been thinking for sometime that I should jump in here and mention Angle of Attack. Glad you did. Flying the correct AoA allows you to forget about a whole host of things and simply concentrate on one. The U.S. Navy has been making aircraft carrier approaches using AoA for decades. They never have to worry about weight, temperature, or anything else. Just fly the specified AoA for the configuration (which usually is simply gear down and flaps full down) and you will be at the optimum approach speed. (That, by the way, is not necessarily the best glide speed.) These guys did a fantastic job of making the best out of a truly horrendous situation but we could give the next crew encountering such a situation some help by teaching them a bit about AoA (and providing an AoA indicator).
BTW, AoA at cruise speeds is not very useful. At cruise it's awfully hard to fly an accurate AoA since the faster you go the less AoA changes with speed changes.