1. Ducking is a hell of a lot more effective at saving your ass than strafing.
2. Building a bunker? Make the cover 2 blocks high. Can't see that derpy lake down there? Build your bunker lower instead of sacrificing invaluable cover (esp now since in beta 36 Rifleshots can't destroy blocks anymore)
3. Do you see your team doing autistic things (building statues to gods you don't want to know, building the biggest ass retard fortress ever at a place where it doesn't make sense, fucking up bunker building etc etc)? Tell them to actually care about the game's content and frankly remind them that "If you want a block based building simulator you should try out Minecraft, not this"
4. Aiming really isn't hard once you get the hold of it. I find both shooting from the hip and using iron sights pleasantly fine.

Will extend this with more Protips for Greenhorns