Men, palm her lower back.
When you are behind her, stimulating her back is one of the best tricks you should know. Stimulating the sacrum (the five fused vertebrae at the base of the spine, often called the small of the back) in this position can add to your partner’s arousal because this particular area is super sensitive. The sacral nerves run from the sacrum to the genitals, as well as through the legs to the soles of the feet. The best way to use the sacrum to your advantage in this position is to tap gently at first with the fingertips of one hand. Make sure you are able to keep your balance.