I'm not sure in this day and age if agents will bargain away rights to a publisher; and maybe this is for those who try to negotiate without an agent; what rights will (legit) publishers try to take that you should fight to keep?
You may want to keep film rights.
You want the foreign rights, too. (I think)
What "rights" do publishers try to take that you should keep?
Real publishers buy rights.
World rights would negate any future foreign rights of course.
No, they don't.
When you sell world rights, the publisher then turns around and sells regional/language rights to other publishers, taking a percentage off those sales for themselves and applying the remainder of the funds first to your advance with them, then funneling the money to you once your advance is paid off.
And that's how you earn out before the book is even published.
Don't be too hasty about thinking world rights is the way to go - I will say William Morris Endeavor is excellent at selling foreign rights, so are other large agencies. Lottery has sold to 20+ countries and those sales have nearly equaled the original advance...just sayin'
Also this entire discussion is a perfect example why a good agent is critical...I won't even get into the complexities of foreign taxes and how my agency has helped my CPA out...