The social world is a biological ladder tournament. Through practice and preparation, you have to put yourself ahead of as much of the competition as possible. Just watch the animal shows on the Discovery channel. We are exactly like them but a little more complicated. We are a herd and you have to fight for your place in it. You have to form a strategy and utilize your time and effort into developing the traits and skill sets that your particular plan will need. You don't have tact? So what? I know a guy who completely lacks it and has tons of friends and get plenty of attention from the opposite sex. He just redirected his effort else where. I also know people that have had similar results completely different approaches. If you are having problems, then you either don't care or can't adapt.
First, cover the basics. Hygiene & basic manners. Get that right and you will be in the top 50% of the competition. If needed get professional help. Salon instead of great clips? Laser hair removal? Spa treatments? Do what it takes to get caught up. Read a book, take a class, or watch a make over show or two if you have to.
Second, get in reasonable shape. Depending on how far you run with it, you can put yourself leaps and bounds ahead of the competition. It just takes time. If it took money, everyone would have it. Go to the closest gym and get a personal trainer. Do whatever they tell you to and stick with it for at least 6 months to a year.
Third, appearance. Looks matter and you have to dress well. Just pic a style and go to the stores that cater to that style and wear whatever the manikins are wearing. Now do it consistently. Its that easy.
If you are half way successful at these three steps you should be ahead of at least 75% of the competition. You can of course keep adding to your social appeal through other talents. Got a little tact? Great, but if not, do something interesting that people can relate to. Preferably, non technical, non science, non school sponsored. Examples - rock climbing, music, art, motorcycles, traveling, skateboarding, gardening, camping, wine, scuba diving, photography, acting, or anything that when you talk about it, people think it sounds fun and interesting. Just pick something.
Do these things and people will come to you. Its that easy if you actually do it but it is a competition and there are always going to be people ahead of you and behind you. You just have to fight for your place. And remember, you have to adapt to the world. It won't do the same for you.
Also, there is a great segment in the movie American Psycho about fitting in.