Although tangential to the actual determination of the issues at play in a case, it is still important to consider how the client will present him/herself in front of the Judge or Jury. The most important consideration is that whatever the client wears, it should show the proper respect to the Court.
Gone are the days when everyone wore suits to Court. Watching 12 Angry Men now, with the juror room full of men in suits and ties is not the norm anymore. This represents a relaxing of sartorial attitudes of society in general, not anything particular to Court proceedings. Now polo shirts, jeans, sneakers, and the like are the standard.
When clients ask what they should wear to court I always tell them to be respectful but comfortable. If a client can wear a nice conservative suit, that's great, but many clients are incredibly uncomfortable in a suit and tie and if he or she fidgets or sweats or otherwise looks out of place that may have a poor impact on the jury. If the client is more comfortable in chinos and a button-down shirt that is acceptable.
Of course it can go the other way as well, if a client projects an image of arrogance by wearing too-expensive tailored suits in front a of generally rural or suburban jury they may draw another adverse inference.
Clothing to be avoided:
Cut-off jean shorts
Adidas workout pants
Budweiser branded T-shirts
NWA concert T-shirts
Footwear to be avoided
Thigh high leather boots
Face tattoos, if applicable, should be covered in makeup concealer prior to entry to the courthouse.