It's not huge, you can pretty much walk around the centre in a day, and the nightlife is infamous.
Quick guide to the areas:
The West End
Bars, clubs and pubs, good restaurants with a Bohemian atmosphere, becoming popular with stag parties looking for a more sophisticated night out.
You can find The West End, west of Prince's Street.
Mainly shops, with old Georgian style roads going North which have some great restaurants and pubs.
Very lively and to memory lots of student type bars and clubs, great places for pub crawling.
The Royal Mile
One of Edinburgh's most visited streets with fantastic late night pubs, cafe's and whiskey shops, if you fancy a late night tipple The Royal Mile is a great place to go.
Is Edinburgh Busy?
As the Americans would say, "you bet your asse it's busy."
Where do you think the song Auld Lang Syne comes from?
What Can I do on my Stag in the Day?
Now you are talking, Edinburgh obviously has Paintball sites, indoor and outdoor karts, quads, rage buggies and all the popular stag activities known to man however, if you are prepared to travel an hour and a half into the highlands you have the best white water rafting in the UK.