This is a description about the function of cooperation as a whole, but also when it comes to powers and skill use!
Working together to build storylines is what a MUSH is about. It is one thing to have a cool idea, but another to get others on board and interested. They need to invest also. Nobody's alone here!
From a scene-specific standpoint and rule of cooperation, balance is everything. Do great things, but enable others to do great things. Permission is extremely important. It empowers all of us to take risks and have stories that can go to dangerous places.
If you're new to cooperative storytelling, I recommend starting here with Chaucer's guide to roleplay. It breaks down a lot of flaws that good players avoid, and traits new players will want to focus on.
To harm (or heal) someone, you need permission from the person you are targeting. See: +news Consent. Period. Sometimes this seems so backwards to people: why would anyone take an injury or be caught EVER? Doesn't it create just a lot of power-players? But this isn't a PVP game where you 'lose' when you are hit. Getting hit can mean MORE story. It can mean your character growing, having reasons to work with others. And this is a social game. That's the heart of this place: stories WITH people. Otherwise you'd be writing a cutscene alone, wouldn't you?
- WITH GREAT POWER (you know the line). Having a super powerful character does NOT give that player more /narrative/ power! Just because Zod CAN do a thing doesn't mean he should, in this style of play. He can get his big powers out on the NPCs and during big plots, though. In fact, powerful characters have a bigger challenge than say, someone like Mary Jane. Because they have to be far more mindful of respecting others; Mary Jane generally isn't going to be doing things that threaten others' ability to be involved, as she can't lift a planet (or even a daily planet). But Superman has to be mindful to not just solve a problem for others, and moderate his heroism so that others can shine.
- WITH MORE POWER... Those who are powerful should also be mindful of other characters' limits and flaws. Those with godlike healing abilities should not be fixing a broken spine for Xavier, or granting a massive magical sword to a character that formerly was street-level, without a lot of good story behind it. Usually such grants should be temporary in nature. Iron Man should not be handing armor out all the time, for example. It is on the player to find a reason to not hand others unearned power boosts, but to act with balance: to reward stories with fun items when reasonable and wanted. Flaw removal is often unwanted: Iron Man might want to keep his chest arc reactor problem, and healing him needs his consent as well as a +sheet update.
- If you have a resource or skill that affects others in an informational way, also ask. Just because you can read a mind and know their secret identity, do not ever skip over the permission of 'can I read this from you right now', or 'can I know this about you, I have a resource that lets me tap into the mother box of world info'. The skill or resource allows you to ask with a reasonable excuse, doesn't allow you to automatically know other player's secrets.
Why listen to any of this? Because the 'currency' of this game is social credits, trust, and mutual experience. Build with others, and that's where the payoff is. It won't happen immediately: you can't just walk into a room and expect everyone to be your close friend right off. Imagine entering a party and getting loudly drunk. Nobody's holding your hair, man. Ignoring the rules means there's nobody left to play with, and nobody should have that experience or wonder why they aren't getting the experience they are after. Expectations just may need to be adjusted: this game isn't always about showing off amazing powers. It's helping others to do so to, and then shining when others put the spotlight on you. And it can be awesome.