1. Fashion - Don't wear any bright color clothes. Not everything has to be black, almost any dark color will work. Experiment with different goth fashions like spiderweb body stocking or skull-print pants. Don't forget the black finger nails.
2. Home - Don't stop with what you wear! As a Goth, you'll be expected to have a wicked-looking home as well. If you can, paint your walls a dark color. Put foil paper over your windows so that no sunlight can come in. Buy dark colored blankets to put over your furniture. Have several candles around the house. A few pieces of gothic art wouldn't hurt. Also it wouldn't hurt to buy a coffin now. Plus, some of the fancier ones can make really nice beds.
Click Here 2 Go 2 Gothic Martha Stewart. ~Tips on how to darken your home~
3. Relationships - As a Goth, you'll probably only be able to date within your little subculture. This also means Goths have their own style of pick-up lines and dating tactics.
4. Language - Know your Goth lingo. The last thing you want to say is "rad." While you're at it, brush up on your vampire history. Avoid using any "prep" lingo: 'as if, whatever, loser'.
5. Hair & Make-up - If you don't have black hair already, dye it. Also if you have bangs you might want to grow them out. As for make-up wear black eye liner and black eye shadow. Your lipstick doesn't have to be black, dark red will work.
6. Behavior - Of course goths don't act like normal people. I think this is one of the hardest things to master. Goths are either angry or depressed. To help you be put in a "gothic like mood" try visiting cemeteries and learning as much about ghosts, vampires, and death as you can. Also pick up some new hobbies like picture taking. Take pictures at cemeteries, of road kill, or of dead plants.