Without a shoddow of doubt, you should go to this place:
http://www.brouwerijhetij.nl/The beer is absolutely top notch and well strong. You never see any tourists in there (unless we're there with some locals - I've got a couple of mates who live there).
My bro used to live in Leiden, which was really nice. It's nice to get out of the Dam. Trains are all good, so getting palces isn't too difficult.
Try to avoid coffee shops like the bulldog and grasshopper (well avoid them if you're buying weed as there's is fairly cr@p). The kandinsky coffee shop in the back streets between Central Station and Dam Square (on your right as you're walking up) is a great place, you can get your gear in the coffeee shop and then smoke it in the pub a couple of meteres away. De Rokerij is also one of my favorite coffee shops (there's a couple of them, but we normally end up in the one near Rambrantsplein).
A lot of night life occurs at the Leidesplien end of town (just say Led Zeppelin to a local, they'll know what you're on about).
