Big point is to always read and understand a contract BEFORE you sign it. Many times, things will be put in a contract just to see if they can get you to sign it. If you request points that go too far to be removed, they're as likely to do it as not. It really is "Writer Beware".
Once upon a time, I submitted to an agent who wanted to rep my work and sent me a contract with several things I didn't agree with. Things like they get a cut from ANYTHING I sell for the remainder of my career, regardless if they sell it or not. I don't remember the other things, but that was the biggie. I called to request she remove that clause and she started screaming at me. I requested she send me my submission back and told her I wasn't going to sign it. She got vulgar with me. i had to get a lawyer friend to send her a letter to get my ms back. Yeah. And to think, if I'd've signed that contract, I'd still be screwed.
I did sign an agent contract when I finished my first novel. I knew the person personally and didn't think a friend would screw me over. She did. Not only did she reserve the right to rewrite anything she didn't like about my work before she submitted it anywhere, she locked me into an exclusive five year contract--if she didn't represent it, I couldn't seek other representation or submit it myself. That was a big learning experience.
AFAIK, both of these agents are out of business (and the first one is dead, actually--I kept tabs). Be careful.