This is the best advice of all that I've read in this thread. I wanted to add that strategically, you definitely want to have that job in hand before you quit.

This is the best advice of all that I've read in this thread. I wanted to add that strategically, you definitely want to have that job in hand before you quit. Firstly, if you're interviewing at other places when you already have a job, they are usually willing to skip references and hire you based on tech knowledge and interviews alone. Grabbing tech talent these days is really tough, and most recruiters know they have to be discreet with people transitioning from a current job. Secondly, the job you're at is likely to give you a crappy reference after you give notice. You want to be well on your way to making that next employer your next reference as soon as possible. The alternative, i.e. being unemployed with them as your most recent references, makes you harder to hire.