One I use on almost every flight: Dependence on weight for approach speed, best glide speed, VX, VY, VA: The percentage change in speed is half the percentage change in weight.
Penetration speed: When gliding with a head wind, increase gliding speed by a quarter of the wind speed. When gliding with a tail wind, glide slightly slower, but never slower than the minimum sink speed.
IAS -> TAS: Two percent per 1,000 ft.
Crosswind correction: 1 knot crosswind per 1 degree correction, per 60 kts GS. E.g., 10 kt crosswind component at 120 kts GS requires 5 degrees correction.