First of all, what knowledge do you have already? You'll need set theory; so that means point-set topology as well probably, since it's really just set theory on steroids. It'd also be nice to know some real analysis, so you can draw parallels from Riemann integration and the real line. Also, if you don't know Riemann integration and start learning it after Lebesgue integration, you might start using properties erroneously from Lebesgue integration.
As for resources, you'll find plenty just be searching the internet. As long as you have sufficient knowledge, you should be able to dive right in to measure theory.