We've all been in this situation. One of your friends wants to be more than friends, but you don't. Here are some of the ways that women can deal with the situation, drawn from my vast experience over the years.
Tell him clearly that you do not want to date him. You now have a delicate balance to maintain: letting him know that you care, but also sending a clear message that he is not special to you like you are to him. Also realize that you can use this situation to your advantage. Here are some suggestions.
Kiss him for 10-15 seconds every time you see him, and be sure to kiss him goodbye (don't let your other friends see this though, as they may not understand). He will really appreciate this because for a few moments he will feel that wonderful emotional intimacy that he craves with you. If he sees this as a mixed signal, explain that you are "friends with benefits."
Invite him over to take a nap with with you. Wear only your underwear, and maybe ever take your top off. He's not one of those sleazy guys that just wants to get in your pants, so don't worry that he will feel teased. Just like with kissing, he will derive great satisfaction from the illusion of intimacy, but make sure your intentions are clear by pushing him away if he tries to cuddle. Lying on the other side of the bed should be enough for him.
Make plans to spend time together. He will love looking forward to it, but don't lead him on, so decide to do something else and don't answer when he calls to see what's going on. The next day, apologize briefly and then excitedly explain how much fun you had the night before without him. He cares about you, so it will make him happy to hear that you had a good time.
Sometimes, despite your best efforts, the guy in this situation will start to get the wrong idea about your lack of feelings for him. You might need to be more obvious about your feelings.
When he calls, tell him you can't spend time with him because you need to spend more time with your dog. He still might not get the hint, so show him clearly the difference between what he wants and what you want. He wants to eat dinner, cuddle, watch a movie, give you a massage, and then fall asleep in your arms. Tell him this is a great idea. Enjoy cuddling and kissing during the movie, but then show him how much his plan differ from yours. When the movie ends, explain that you really need to get started on your taxes because the deadline is less than a week away. Keep a straight face. He'll slowly realize how different your feelings are than his, and that you want him to leave. He might express some confusion and disappointment that causes you to feel guilty, so make yourself feel better by saying you'll come over to spend the night when you are done. After he's gone, go ahead and go out or do whatever you wanted to do. Call 3 hours later and say it's not going to work. The next day, make a point of mentioning how you still haven't done your taxes.
Now, sometimes, even after all this, a guy will still not understand that you just want to kiss him occasionally, and that's all. At this point, you've done everything you can to say that you just want to be friends (with benefits). Any further emotional pain on his part is out of your hands, so you might as well get what you can from the situation. For example, let's say you wanted to go out with some friends Friday night, hit the bars, maybe smoke with one of the other guys that likes you. But this isn't starting until 11 or 12 Friday night. Meanwhile, your roommate is gone for the weekend and you'll be home alone with boring errands to run. Now's your chance to leverage that guy. Tell him that you're home alone the whole weekend and that it will be a good time for him to sleep over and spend time with you. Invite him over for dinner, and to make sure he shows up, tell him you want to get a couple bottles of wine to drink together after dinner and "see what happens." It will work for sure. Just make sure you don't mention your plans. When he shows up, explain that you have some errands to run and invite him along. He loves spending time with you, and you hate standing in line at circuit city all by yourself to get your camera fixed. A win-win situation. Grocery shopping is also way more fun with two. You also need to get a cute new shirt to wear when you go out later, and some sexy new underwear. He's happy to help you pick something out. Buy him some boxers. He'll love it. When you finally get home, model your new underwear for him. He'll tell you how sexy you look in it, which means you'll be glowing with confidence when you go out later. Break out the wine, pop in a movie, and cuddle up on the couch until it's time to go out. Trade back massages, those are always relaxing. Your friends might call to ask when you're meeting them. Be discrete so the guy doesn't catch on. Tell him right after the movie that you're going out. He's going to be upset, so play it like you just need to have some face time with some people and that you'd like to get together later. He'll believe you. An added bonus of this plan is that now you'll already be a little drunk when you meet up with your friends. Now go out there in your sexy new outfit and have a blast.