Most suitable uniform is a warm GENUINE smile (rather than a smarmy one, practise in the mirror!)
Wear a suit Steve - first impressions count. Stop thinking like a tradesman, turning up in your "shabby" polo shirt might be acceptable to you but not to sdomeone who's used to dealing with people wearing suits. When in Rome....
What you LOOK like as you walk in the door will dictate whether the receptionist will take you seriously when you open your mouth. Seriously, it's that fine a line. If you look scruffy she'll have decided as soon as she sees you, before you've even got to the desk, that she's going to fob you off.
The rest is an art that only you can teach yourself.
A hint: start at the ones you'd like to work for the LEAST. This way you can get over the brown trouser syndrome without much at stake. You'll be a bag of nerves and stumble your words out, you won't be very confident or assertive and if they say "go away" you won't have the balls to stand your ground, you'll just whimper "Okay then bye" and walk out the door.
Cut your teeth where it doesn't matter and then once you're confident pick some juicy looking ones and move in for the kill.
Good luck
