Slow. It. Down.
Feel yourself pulsing inside of your partner. If you have a vagina, clench and release yourself. Kegels feel amazing on a penis. Breathe together. Kiss their forehead. Touch noses.
Add stimulation to the fun by using your hands. Ladies, reach a hand down there and rub, stroke, and tickle his testicles and inner thighs. Feel the small of his back, and crawl your fingertips up his spine to the nape of his neck. I once had a huge beast of a man who loved to lightly cup my ears and stroke my hair. I've never forgotten that, and have since learned to pass on that tender move.
Count to six S-L-O-W-L-Y while moving carefully into your partner. Not only is this strikingly intimate, you'll be able to feel more -- and if you sync your breathing, you're more likely to simultaneously orgasm.