Some of the popular gothic style traits:

anything black (White or any dark colors like navy blue and deep red are also popular but less common.)

silver jewelry

pallor (This could be because some Goths want a sort of undead look; or they want to embody the Victorian aesthetic that says pale skin is a sign of nobility; or because tanning causes skin cancer. In general, Goths view paleness as much more aesthetically pleasing than being tan, whether or not they have a reason why.)

dyed hair (Black, very light bleached blonde, red, or purple are fairly common.)

black and white makeup -- white foundation, black lipstick, black eyeliner

thin, plucked eyebrows or shaved off and drawn in eyebrows

bondage and fetish fashion -- leather, PVC, latex, rubber, vinyl and bondage gear, corsets

crushed velvet or regular velvet

poet's shirts -- a few ruffles around the cuff, the collar, and the front (They are usually white.)

chokers -- a dog leash with spikes, a bondage collar, or a velvet ribbon tied around the neck

ankh (Egyptian symbol for everlasting life)

the Eye of Ra (also, Eye of Horus, an Egyptian symbol. The symbol's popularity with Goths is partly due to the fact that it is on the cover of the "Vision Thing" CD by The Sisters of Mercy.)

pentacle (The pentagram is a five pointed star -- a pagan symbol for fire, earth, air, water, spirit. The pentacle is basically a pentagram with a circle around it. These terms are often used synonymously. Since the pentacle is associated in some people's mind with Satansim, some Goths may wear a pentacle to shock people, or as a part of their Theatrical Satanism.)

wearing lingerie that shows (garters, teddy, bustier, slip, camisole)

opera-style capes or cloaks

opera length gloves, either satin or latex (shorter length gloves as well, usually vinyl)

crosses (Christian symbolism)

fishnet tights or shirts

black and white horizontal striped tights like the Wicked Witch of the West

chains (as a belt, necklace, part of the outfit, whatever)

spikes/studs (usually attached to a leather jacket or to a collar, belt or bracelets)

tattoos (depends on the person)

piercings (Usually not as excessive as punks, goths might have a few piercings, if any. Tongue, nose and nipple piercings seem most common. It depends on the person.)

pointy toed shoes, buckle boots, high heels, combat boots or Doc Martens

a short A-line haircut or ratted out, hairsprayed, chaotic hair, sometimes hair extensions

a leather jacket (often with designs painted on it), black trenchcoat, black vinyl raincoat-looking jacket, or velvet jacket
a box (A cross between a small purse and a lunchbox, usually black with silver hinges and a briefcase-like handle. They are usually decorated with band stickers. Guys and girls alike carry them.)

Some Goths tend to look like: Robert Smith (of The Cure) -- ratted up hair, smudged red lipstick, black makeup for eyeshadow; Siouxsie Sioux (of Siouxsie and the Banshees) -- short black ratted hair (or a sleek A-line haircut) and the makeup done very precisely with pointed angles; Death (the Sandman comic book character) -- designs drawn around the eyes, tousled black hair, always wearing an ankh; Eric Draven (character in the comic book and movie The Crow) -- white face with black vertical lines drawn above and below the eyes, black lipstick drawn extended past the edge of the lips in long smiley face sort of lines, black trenchcoat; Andrew Eldrich (of the Sisters of Mercy) -- always wearing sunglasses, short slick black hair, leather pants, a leather jacket with an open shirt; Bettie Page (1950's bondage pinup queen) -- long wavy black hair with short, curled-under bangs, very thin drawn in eyebrows, and dark red lipstick.
Vampire archetype -- Lestat or Louis from Anne Rice's novels The Vampire Lestat and Interview with the Vampire or a Dracula influenced look. The vampire archetype look also contains some commonalties with the vampire-free Victorian aesthetics: elaborately designed hair, ruffled shirts, long skirts, velvet, opera capes, corsets, vests. Punk archetype -- ripped tights, chains and spikes, a leather jacket, boots, ratted hair, defiant attitude. Tortured artist archetype -- a bohemian influence, wearing all black, maybe kinda beatnik, wearing sunglasses all the time, maybe a beret, thin, tired-looking, a notebook carried around at all times, can be seen reading alone in coffee shops. The tortured artist look may be a little more avant-garde, but it is not quite as clearly defined fashion-wise. It is made more by how someone acts than how they look.

For guys, some common Goth looks are:

A fishnet shirt and vinyl or leather pants with some sort of boots and other various accessories.

A white shirt (sometimes with the collar folded up to cover the neck), black pants, a black vest, boots or dress shoes.

Some of the guys will wear makeup, skirts, corsets or heels. It's not really meant to be cross-dressing because they are not actually trying to look like women. Gothic tends to be a very androgynous thing, where some of the straight guys like to look or dress feminine, either to challenge social gender barriers, to show that they have an open mind, or as just a fashion thing.

For girls, some common Goth looks are:

A cleavage-enhancing corset top with a long, flowing or tutu-like skirt.

A crushed velvet dress with either boots or heels.

A fishnet shirt with a black bra underneath, a bondage belt (or some other type) and either 1) a short vinyl skirt 2) a long velvet skirt tight leggings or stirrup pants usually made of vinyl or crushed velvet.

Fishnet stockings with a vinyl dress, bondage gear, high heels or heel boots.

see: "Getting Started" in Gothic forum