Have you ever been playful and just out of the blue, made the squeeze play? For us guys who love nipples, it's just a friendly way to introduce yourself. CAUTION!!! ONLY do this with guys who are receptive.
The nipples are a guy's most sensitive part of his body. For me, they cause immediate arrousal. It takes almost nothing to get them hard. They seem to grow more the more attention they get. They seem shy at first, nuzzled beneath chest fur, but they almost instantly sprout magically to provide pleasure to the body. However they seem to get no respect in the realm of foreplay.
So is there a right way and a wrong way to turn these dials? Yes there is. Don't play with them so hard that they become raw.
They are tender and sensitive, that's why they feel so good when aroused. Do brush them to their point of hardness and they lightly squeeze. Lip service is definitely desirable in this case.
If you see a guy with nipple clamps, it may seem like an open invitation to play, but please ask first. He'll respect your manners and will return the courtesy in kind.
The holy grail for nip lovers is a webzine called Holy Titclamp, run by Larry. He wrote the gospel on enjoy your nips. His writings are both useful and amusing. Also like mined guys join Nippleplay.com. Check it out the next time. I'm sure your nips will thank you.
Hopefully this post will prove useful to guys who never explored their nips. By giving them all the attention they deserve, they'll never let you down.