Most Helpful Guy
Tube/shorts would get you lots of free drinks then a ride to someone's bed fast
1. go with 1-2 gal friends - never get out of view of each other
2. dress as if coming from work (secretary-executive) the first time
3. be friendly but dismiss anyone making you feel uncomfortable and move on, make room for someone else more suitable
Most Helpful Girl
What type of pub is it? Like a quiet local, or a music pub, or club pub, or one that is part of a chain (like Wetherspoons), or a friendly family pub, or country pub?
(I'm guessing from the word pub you are UK?)
If it's your first time I would go in a dress, or a skirt and top combo. Purely because it's safe and you can see what others wear. Most of the pubs around me are jeans and shorts places but there are a few where being a bit more dressed up is an idea. There are nightclubs around me where no trainers are allowed, and one is even formal wear only!