The first few moments can be painful. Make sure you are relaxed and use plenty of lubricant. The feeling is great while you're doing it and then the next day feeling the sensations as your ass works itself back into it's tightness...mmmm. I love it.

Have your guy use one finger first, then two, then a vibrator just to loosen you up. It'll make it easier for him to push his way in.

ENJOY!
MB