How? Here are a few things that have helped:
1) I got lucky - I jumped on something early and got picked up quickly and rode on the back of a giant gorilla as it kept getting higher and higher - right place, right time
2) I keep costs low - I use Tumblr (free) and cheap, pluggable services like Campaign Monitor, Wufoo, Buffer, and IFTTT to automate a lot of the process.
3) Don't be afraid to ask for money - I started doing this very early on, but even that wasn't soon enough! People will pay if there's a benefit, so don't be afraid to ask.
4) Keep it simple - I write brief emails, I don't respond to everything and I only spend a few hours each week on the site - updating content, checking stats, emailing etc.
5) Get multiple sources of revenue - I use a number of affiliates as well as offering traditional advertising.
6) Be social - Twitter, Facebook, Tumblr, Pinterest, Google+ - BWB is on all of these. I try to engage with people and respond to things
7) Start a mailing list - this is not to be overlooked!
I hope this gives you some helpful ideas :) don't be afraid to ask any questions.