I'm thinking specifically of dates, where you won't be wearing a suit or anything terribly formal, but still want to give off the impression of being successful, stylish, handsome, and hip without being overbearing. I have no intention of actually becoming well-dressed, but I figure it'd be nice to have a couple of outfits that show that I do, in fact, clean up pretty nicely.
That said, if you bought all your clothes from j.crew and maybe some hoodies and t-shirts from american apparel, you'd be covered for 98% of north american dating and office working situations. (losing out on dates with extreme hipsters, goths, gutter punks, fashion plates, ravers, nudists, hell's angels, and the amish)
Bear in mind that like any community it has certain strong personalities that set the tone for everyone else. If your instincts say "following this advice will make me look ridiculous" then you're probably right.
In my experience, having a female friend you can get rapid feedback from is invaluable, too.
A decent clothes store. Most people working there will be more than happy to give you tips and pointers. If you want a more complete package, many stores will let you book a time where one of their stylists will give you their undivided attention and work with you to put together a complete wardrobe.
I think I am pretty familiar with what it means to be badly dressed, but well dressed such that it might induce the opening of doors is hard to pin down.