I made plans first: consulted w/lawyer, got advice, made copies of income info, retirement accts, took pictures of all the assets (furniture, etc)...then told him.
And a good thing, too. He has since hidden assets, lied about income (he's self-employed), and generally made every sneaky move possible so that he doesnt have to pay child support. Which I expected from him.
It took me 3 months to get all the paperwork in order and plan my exit, and even with a considerable amount of planning, things went fairly awry when I finally told him. He blew up completely (didn't even see it coming, though I had moved 75% of mine and ds's belongings out of the house already - and he hadn't noticed!) - anyway, he yelled and stormed and threatened all sorts of things about police and having me arrested if I took ds out of state (he knew I was going to go stay w/my mom out of state). In the end, I just left w/ds, and ended up leaving a bunch of stuff behind that I hadnt gotten out of the house yet. Like the photo card that had all the pics of the assets. I also forgot the copies of his retirement accounts, and some of the past taxes.
I also made sure that ALL of my very important personal items were safely in storage, or with a trusted friend/family member before the s*it hit the fan, so to speak. I shipped my grandma's quilt, my & ds's baby books, my childhood items, important paperwork (birth certificates, car title, etc). I am so glad I prepared the way I did, or these things would probably be lost to me at this point. He refused to let me back in the house until court ordered, and then a bunch of my things were gone. But I got what was important, so I didnt care much. (Except that some of the things that he hid were fairly valuable marital assets.)
I dont mean to freak you out or sound alarms that may not even be pertinent in your case, but a little prep never hurts. And I would advise that you talk to a lawyer first, just so he/she can tell you how is the best way to proceed with filing, serving, whether to stay in the family home, etc.
ETA: Oh yes, definitely transfer 50% of joint money in YOUR NAME only.