Many Marks Hunters don’t know how to properly engineer the first few moments of a raid encounter. I'll be honest I fall down on the job many times. Its a lot to remember, its a lot to execute. But the more you work it the easier it gets.
First thing is first, communication in your raid. You need to be aware of when your tank intends to pull. Its also important to know when they plan on burning Heroism/Bloodlust. Nothing is more depressing then hitting Rapid Fire and then hearing that sound...the sound of arggggggggghhhhhhhhhh I just wasted a cool down.
Before the pull begins, you should have your Hunter’s Mark up. Wait to put it up for as long as possible because in a short encounter you don't want to waste a global cool down throwing it back up. If it’s a longer encounter, you’ll need another – find a situation where you can sacrifice a Steady to renew it, or even better, find a situation where you can't DPS like right before Putricide’s Tear Gas and do it then. Also remember if someone in your raid has Imp Mark you no markie.
Okay back to the start of the fight discussion. You’ve marked your target and you’re ready to go. Fire off Misdirection on the tank who is pulling. This puts you on the clock and you must pull in the next 30 seconds or you’re gonna have insane aggro problems. I get very nervous about it and pop my MD after the tank has pulled. Not wise but I have timing issues. When your tank begins their usual count-in to a pull, get your Speed potion ready. You absolutely must make sure you pop this before combat starts. If done properly your potion cooldown will still be ticking even though combat is engaged. This is known as pre-potting. Remember that it is worth it to sacrifice a second or two of pre-potted time by using the potion early than lose your second potion by popping it too late. Learn your tanks styles and mannerisms and learn the encounters to know if there’s RP before the encounter that basically gives you a cue. The start of the Jaraxxus fight in ToC is a good example of pre fight RP
Combat has now engaged. The first damage action you take is to put Serpent Sting on the mob. All supporting buffs are will not be up yet, but do it anyway because you’ll be refreshing this sting. About a half-second before the GCD ends, blow your cooldowns. Call of the Wild, Rapid Fire, everything. Remember that these next 10 to 12 seconds are being buffed by your pre-pot so you want to maximize it.
With cooldowns running, your GCD has now come up so fire Chimera Shot. You've already started your Misdirection with your Auto that fired due to Serpent, but you’ll get this Chimera and the immediately-following Aimed in before MD expires. You’ve now been in combat for 4 or 5 seconds so on your next global cool down fire a new Serpent Sting. Why? Because your DKs, Moonkin, or Warlocks should have applied their 3% magical damage increase (Ebon Plaguebringer, Earth and Moon, or Curse of Elements). You need that 13% boost to Serpent Sting, and you want to fire it now while you’re still in your pre-pot.
The timer is at six seconds so go ahead and get off three Steady Shots. That puts us at 10.5 seconds. Wait for Chimera and Aimed Shot to come off of cool down, then fire them as they do. Do not try to squeeze in a fourth Steady it’s better to wait for a Chimera and Aimed pair than to push them back for a Steady Shot. Assuming you’re hitting your GCDs properly you’re going to be at around 14.5 seconds and Rapid Fire should be fading within the next second. The next GCD after your Aimed Shot all of your big damage abilities will be on cool down so hit Readiness.
16 seconds in the fight and everything you need is online again. Pop Rapid Fire as soon as you notice the buff fade. Then start your rotation again Chimera, Aimed, and 4 Steady Shots. Your pre-pot will end right about the time you hit Readiness and by then you’ve gotten its value – either a handful more Auto Shots, faster Steadies and ridiculously high crit-rate Serpent Sting ticking on the target that will be maintained with Chimera Shot through the end of the fight.
Three minutes later, your Rapid Fire and Readiness are going to come off cool down so rinse and repeat. No doubt this is a lot to remember but practicing on a target dummy and keeping a little note by your monitor helps. Marks is a tricky spec and it takes some attention and care to play it to its full potential. Do your raid a favor and put in the time to get it right.