I've been doing some worldbuilding on my contemporary paranormal (werebears) and it's been going well. I slid back a little when I was on/got back from my holiday and I've only just managed to start picking it up again, but I'm confident that I can get a good portion done by the weekend.
One thing I think it's important to avoid is an overabundance of research. Reading a couple of books to get an alternate view is good, but I know that I personally need to avoid the trap of "research, research, research" - because it'll either be too easy to put off the writing or I'll be tempted to add too much detail.
So, read some - write a lot, and don't go overboard!