I posted this on the Freelancer forum a while ago:
Dressing well is extremely important. This was driven home for me a long time ago when I went on a shoot where I was better dressed than the producer. He was wearing a T-shirt and cargo pants. I was wearing a button down shirt and some new black jeans. The client kept talking to me and asking me questions. I kept responding, "I don't know, why don't you ask the producer?" gesturing towards him. The client kept trying to talk to me any way because I looked more professional.
I always try to look presentable, but also be comfortable. I generally try to wear dark colors to a shoot so I don't reflect any colors, or get caught in a window reflection. That's why I prefer black pants over khakis, and dark shirts.
On a news shoot I know that on the same day I might be walking in to the capitol building, a swamp, or both. I try to be prepared for any thing.
Normally I wear a wicking polo shirt. New Balance sells some labeled "Lightning Dry" here at an outlet store and online. You can also find them in golf stores. I think they're great. I get hot very easily and I tend to sweat
a lot in the summer to the point where one producer actually asked me if I had another shirt in the car! That's not a problem in these. Dark colors also help hide sweat by the way. I have a whole closet full of them now.
I also usually wear nice convertible cargo pants. They have legs that off at the knee (i.e. they turn in to shorts). Nike makes some good ones under the ACG brand. I find them at Dicks. REI sells another version I like. I'm sure Cabellas and pretty much any other outdoor store has them too. Just search for "convertible pants."
When I worked in local news we had a dress code which included pants unless it was over 80. I could wear those pants in to work and the suits were happy that I was properly dressed. Then when I left I could zip off the legs if I got hot, and be happy that I was now properly dressed.
Some times I wear black jeans, or even slacks depending on the shoot. I never wear any thing with holes or tattered edges on a shoot.
For shoes I generally wear waterproof hiking sneakers. Nothing too garish. You never know what you'll be standing in, or where. At the least they keep my feet dry when shooting in the snow, or walking across a dewy field.
Dress like a grown up. = Get treated like a grown up.
It works in the real world too. I find I get much better treatment at the airport, the doctor's office, wherever, if I dress well. I hardly ever wear a non collared shirt in public any more.