What are the precautions to be taken while stimulating my partner clitoris during intercourse?what will happen if we stimulate it vigorously for long?

Ouch!: The clitoris is a small item that packs a "big" punch for its' owner. However, it is very, very sensitive when aroused and is NOT like a penis in that condition that can be "used and abused". Therefore, gentle movements guided by the "owner" or the "owner's hand" over your hand is a good place to start. She will tell you what works and what doesn't, after all she is the "owner" & you're leasing.