For beginners, the most important rule of thumb would be to set themselves up for a strong jump. A beginner shouldn't really be expected to set the horse up that much, as the jumps shouldn't be high enough to require that much control, and the horse should be experienced enough to have a fair idea to what it's doing.
The rider should focus on developing their balance and their strength. Work with a trainer to ensure your position is correct.
Keep your eyes up and look at the jump until it disappears, then look up and keep looking straight. Find your track and rhythm.