These are some of the things I do that will always help, no matter who you are.

1. Go to the gym, even if only a few times a week. To really look your best, or at least close, you're going to need to be in somewhat respectable shape. Even a small effort is better than none.
2. Same idea as #1, but with your meals. Make a respectable effort.
3. Whiten your teeth. Even if you brush when you should, sometimes shit like coffee can discolor your teeth over time. Even like $15-20 dollar generic strips used for a week make a good difference every once in a while. Also try to buy the toothpaste that helps whiten.
4. Buy the Aztec Secret Indian Healing Bentonite Clay, or whatever bentonite clay you want. Mix it with apple cider vinegar and leave on for 45 minutes. Afterwards put some good moisturizer on your face and repeat as often as you feel the need too. Some of my friends used to give me shit about doing this, but it's funny how a lot of them began using it shortly after. Do your face a favor.
5. Tan if you can. If you really want to look the best you can, try to stay somewhat tan if your skin can handle it. Don't be sleepin' in tanning beds and shit, just keep it reasonable.
6. Try to keep good overall hygene. Wear deoderant, shower, etc... Don't be the dude that stinks. Stay fresh, y'all. You won't be found attractive if you smell like a nutsack everywere you go.
7. Keep good hair. Find what works for you and have fun with it if you can.
8. Dress well. Everyone has their preferences, but if you want to be considered attractive by people I assume you probably want to be considered attractive by, a few decent sets of clothes will do the trick.
9. Don't be a dick. I know, I know, there's always the people (The bro's who enable the ho's, and the girls who tolerate the dickheads) who may not fault you for being a shitty person, but you don't want to be like that. Be nice. It doesn't mean you're not the fuckin' alpha brah in the den or some horsecockey, but rather that you don't need to be a bully or dickhead to feel good about yourself. Smile. Be friendly. That is attractive. Don't stand in the corner with your fuckin' Afflication shirt and chest puffed out wondering why all the girl aren't interested in you.
   

Good luck.