How Sharp to Dress?

Not every industry is a suit-and-tie industry!  Trying to look like a top exec when you’re a skilled programmer is likely to cause people looking for programmers to pass you by — thinking that you’re a hiring manager rather than a worker!
So as you prepare for your conference or trade show, be thinking about your goals and the situation you’re going to be going into.  Focus on four basic fundamentals:

• Industry and Type of Conference
• City and Country
• Climate and Activity Schedule
• Your Position and Goals

Industry and Type of Conference
Think of your industry in broad strokes:  is it conservative?  Trendy?  Way out on the exotic fringe?
You want to fit into at least the broadest possible characterization you can think of.  No matter how sharply turned-out it makes you look, a suit and tie is going to look out of place at most gardening and landscaping seminars or dog training exhibitions.  Give a nod to reality before pulling out all the stops on your wardrobe.
The type of conference you’re attending is also relevant — a half-day seminar followed by a dinner event means social dress, while several full days of panels and talks would call for a more formal business standard of dress.  Neckties up until dinner is a good rule of thumb in most business climates, while evening outfits should be a little more relaxed.
City and Country
While the conference guests set much of the tone, it’s worth remembering that every hotel or convention center is a product of its environment.  The staff and the other guests will play a part in how you look as part of the crowd.
American settings are, generally speaking, less formal than equivalent events in Western European or South Asian countries, although large cities are an exception.  Within America you can safely expect New York and the east coast in general to be the most fashion-conscious sites.  Since everyone there will be well-dressed, it behooves you to wear your business attire plus a touch or two of fashion — a pocket square or an interesting cut of coat, say.
Large convention centers in other American cities tend to be by and large indistinguishable, in terms of fashion environment.  Dress neatly and well within the boundaries of your profession and try to avoid seeming too much of a dandy.  Good style is already eye-catching — you don’t need to be ostentatious on top of it, particularly in Middle America (I love you Iowa).

Be prepared to meet outside - even if you're deciding the fate of the free world.

Climate and Activity Schedule
Your basic hotel setting is climate-controlled — sort of a no-brainer.  Long sleeves and a jacket will usually be fine, though the jacket may need to be light, particularly in the winter when indoor temperatures are raised.
If the conference moves beyond the hotel, however, or takes place at a compound of multiple buildings, be sure to take exterior temperatures into account.  A good suit loses its appeal very quickly when the wearer is sweating and flushed.  Even if 98% of your time is spent in a hotel you’ll need to prepare differently for Las Vegas in June than you would for Boston in February.
How active you plan on being is also extremely relevant — some clothes are comfortable to sit in for hours and others are very definitely not.  Your conference clothes should always fit well enough that you can both move from place to place briskly in them and sit for several hours if needed.
If the schedule includes multiple events over a long day, a change of underclothes or even shirt and jacket may be worth bringing.  A quick change of undershirt at a convenient lunch break doesn’t seem like it would make any visible difference, but you’d be surprised how much better a man who can sit comfortably looks that someone who’s fidgeting with his clothes.

Can you spot the lost tourist? What about the busy business exec?

Your Position and Goals
The key question in all of this:  what are you trying to accomplish at the conference?
Most people will usually fall into one of two basic categories:  shopping for people or selling themselves.  Broad terms, but they’re basically applicable whether you’re interested in hiring workers, landing a job, or just building useful contacts that can help you achieve long-term goals.
Dress to represent yourself as what you need:  an employer, a potential employee, or just a savvy figure in your industry.  Hiring managers may want more of a “power” look with navy blazers and bright ties, job-seekers will need to look traditional and respectable in conservative colors and patterns, and self-promoting experts can always use a few original touches in their outfit.
The key to remember here is that all of these people are always, always, always selling themselves.  Even a well-placed man who likes where he is in life can always benefit from looking like the right guy to talk to.