Depends on who I was trying to impress. It's not something I usually do, but I'd dress appropriately - e.g. for work-related things - or where certain dress codes are observed.
My friends usually find me in filthy jeans and boots, but I'm spick and span by evening time.
I can't say i ever set out to make an impression, im just me!
As the saying goes though, "you never get a second chance to make a first impression" so true but to me you should just be yourself.