Here's the blurb I always post when people are looking to share a fishing charter with strangers. It's a list of things the two parties should discuss/decide upon ahead of time so that everyone has the same expectations and no one is disappointed.
1) If your new fishing partner doesn't show up in the morning, are you prepared to pay for their 1/2 of the trip so that you can still fish that day?
2) When the first fish hits, who gets to pull it in? And in what order will the anglers on the boat take turns pulling in fish? How will you feel if fishing isn't great that day, and you don't get a turn at the rod pulling in a fish? Will you be okay with that? Will everyone on the boat be okay with that?
3) Are you and your fishing partner interested in fishing for the same type of fish? What if they want to go after marlin, but you want to pursue tuna?
4) If fish are caught and kept, how do you plan to divide them up? Will all the anglers on the boat share the fish equally, regardless of who pulls in the fish? Or does the person who pulls it in get to keep it for him/herself?
5) If your fishing partner is a "cheapskate" and doesn't tip the crew, or tips them poorly, are you willing to cover their portion? Or, are you morally okay with the capt/crew getting shortchanged?
6) What if your fishing partner enjoys getting drunk/loud during the trip, and that's not your style? Will you be annoyed, or able to just go with the flow?
7) If your fishing partner gets really seasick and can't fish, will you force him/her to "suck it up" for the full day charter, or will you take pity on him/her and return to the dock?
8) If you catch bill fish (e.g., marlin), do you plan to release them?
These are things that people should discuss with any potential fishing partners to ensure that everyone is on the same page.