We want you in the group where you'll have the most fun. While doing so, also respect the rest of the group and what they're doing:
Show up prepared and on time (gemmed/enchanted/reforged, flasks, food, no interruptions, etc.).
If considering a move, inform your raid leader early, so they can make adjustments before you leave. Help make any transition as smooth as possible.
We have just a few rules for how our raid groups are run, and outside of these, you're free to run your group however you like. We have no restrictions on how you choose your members, or how you do loot, or really much of anything. Do whatever works best for you and your group.
However you choose to run your group, ensure everyone there knows and agrees to it.
Typically this is just 'loot rules at start of raid'. But might also include: how spots are filled, substitutes, attendance requirements, min gear level, experience, breaks, etc.
Do it early, so no surprises/drama later. Preferably at raid start, but definitely before getting people saved. (Your regulars will already know these, just don't forget about subs and pugs.)
Player Moves This rule is about finding a balance between these often-conflicting points: a) players should, with minimal 'hopping', be allowed to find their 'best-fit' group, and b) due respect should be given for other groups and the players in them, by ensuring they continue to be viable and stable.
Never attempt to recruit directly from an existing group. If they answer a 'public' recruiting message, that is great - just don't cherry-pick from another group, passing your group's roster problem on to theirs.
When a potential recruit is from another group (as is often the case), that discussion starts with the player and both raid leaders. All three should work together to get that player where he'll have the most fun, but with minimal impact to the group he might be leaving. Give the other leader a heads-up, so he has a chance to adjust and time to work through the transition.
If the player isn't willing to let his current leader know he's 'looking', then the discussion stops there. (If they can't be honest with their current group, they're not welcome here.)
Be tactful and understanding with the other raid leader. You're causing more work for them, so don't be surprised if they're not exactly 'happy' about it. But if they just can't recognize they don't 'own' that player, well at least you tried.
We're talking primarily about 'set' raid groups, where each 'spot' in the raid group is 'taken' by an individual that, barring the occasional real-life conflict, will always be there to fill per the regular schedule.
Applies less, but still somewhat to, subs and more 'flexible' groups.
Also applies to regularly meeting battleground groups, but somewhat less so due to their more flexible format.