You get a lawyer who is familiar with literary contracts. Look, no one is going to jeopardize a deal to post their contract for other people to see. Frankly, even if I could, it wouldn’t be anyone’s business.
If you’re offered a contract, do your research. That doesn’t mean you get to see other people’s contracts. All reputable publishers give you a good idea what they are offering. Besides, even if you saw James Patterson’s contract, you wouldn’t get the same terms. You wouldn’t get his advance.
So if LitFire or Inkitt or someother - in my opinion - less reputable publisher comes knocking on your door, a simple google search will tell you what you need to know about that publisher.