What are fashionable clothes fro an 18 year old guy ?
My first bit of advice: stay clear of tacky teen brands like AE, Hollister, Abercrombie, etc. They're just that; tacky. They thrive on overpriced, ripped-up logos and cater to wannabe preps.
Other than that, try a cardigan. Your guy friends might call them "gay," but they're great and (more importantly) girls love it when I wear them.
You can wear a tie casually with an untucked oxford (top button undone) and a pair of jeans with some Converse (All-Star or Jack Purcell) or Clark's Desert Boots. If it's colder, throw on a cardigan or sweater for an instantly put-together, but still relaxed look that'll earn you respect wherever you go.
Keep denim dark and non-"distressed"- it's a clean, sleek look that makes even simple weekend looks more sharp and crisp.
Lands' End Canvas
L.L. Bean Signature
J. Peterman Co.
eBay (Great for killer vintage stuff and discounted new stuff.)
No Star Clothing
For more style advice, go here:
J. Crew (They have a men's style section, called something like "Jack Knows Best.")