A question that come up a lot is "where can i vape"?
In the UK it is not illegal to use e-cigarettes / personal vaping devices anywhere but it is becoming more and more common for various places to ban the practice.
The main things to use when thinking about it is common sense and courtesy, you wouldn't smoke a cigarette in the middle of a shopping centre or a cinema so it's probably wise not to blow clouds there either.
Many pubs, restaurants and similar establishments will have a no smoking policy which will include vaping but there are plenty out there that will happily accept it too, courtesy would be to ask the manager / owner if they mind, and maybe the other customers sitting near you.
Vaping at home or outside in open spaces is your best bet unless you check, nobody wants big custard / menthol / fruity clouds blown in their face while they are at the theater or similar.
A wise man once told me, never vape where you wouldn't fart! and that doesn't mean those of you who are loud and proud!
Because of the cloud of vapour you also won't be able to blame the dog or your granny either!
Most people will tell you (hopefully) politely if they mind you vaping, and the last thing we want to do with all the negativity e-cigarettes get in the press is to wind people up by being of the opinion - "It's not illegal! i can vape wherever i want!"
It may not be illegal, but be courteous to others and i'm sure you won't go far wrong.