On single pulls, always start with Tomahawk or Shield Lob. If you do it at max range and run in, the GCD will be up when you get into melee and Tomahawk/Shield Lob generate about as much enmity as Inner Beast does (IB is not something you want to use for enmity purposes; it's worse than a t2 combo attack). For multitarget pulls, facepulling and immediately AoE spamming is sometimes the better option since facepulling starts the fight at closer proximity allowing you to cluster enemies more effectively (and lets you generate enmity on everything right away instead of having 2.5 seconds for HoTs to pull attention away from you), though pulling with Tomahawk and moving into AoE spamming is probably best when the group is spread out from the start.
Beyond the absolutely starting attack, the best starting attack string I've found for WARs is BB combo>SE combo>(Vengeance)HS>(Unchained)SS>(Berserk)BB>(Internal Release)BB combo>BB combo>any of your combos>Inner Beast. For the "any of your combos" portion, BB combo gives you the most enmity but you lose Maim and don't get any debuffs; SE allows you to lead into the post-pacification combo with Maim up and get the 11% extra damage/healing on IB; SP gives you Maim and the 10% damage reduction.
The enmity you generate from that initial attack string (especially if you use BB for the any) is obscene. In t5, after killing the adds, I've swapped targets to Twintania, used that combo, and oftentimes I'm directly competing with the MT's enmity (and sometimes overtaking them if I get lucky with BB crits) even though they've been wailing on her for 30-40 seconds. The only "risky" part is the first 2 combos since you're only opening with a single BB combo and an uppity PLD in Shield Oath, FoF, and RoH spam can pull off of you, but, in my experience, even when they're doing that, they only pull it off for half of a second and are immediately left in the dust by the uber buffed BBs.
For AoE opening rotations, I'll do one of two things. In some cases, I'll Infuriate before combat and immediately Steel Cyclone when stuff is clustered with facepull or Tomahawk followed up by Vengeance and 2-3 Overpowers before going into ST rotation (target swapping to get SE debuff on targets) and using Steel Cyclone when it's up. Other times I'll just start with Vengeance and Overpower 2-3 times, go into ST rotation (SE debuffing) til I get my first 5 stack of Wrath then I do SC>Infuriate>SC. The first is more frontloaded, but the second is more damage and enmity overall so the choice between the two really depends upon how bursty I expect the group to be. Vengeance is an important part of maximizing starting enmity for AoE pulls, in my opinion, because it reduces healing required (which means that you have an easier time keeping aggro off of healers who are the problematic ones for the first couple combos worth of AoE) and gives you an extra 50 pre-stance potency per GCD (or so) on everything (not to mention the comparative damage increase; Overpower is only 120/GCD to everything; Vengeance acts like a ~40% increase in damage when you're AoEing).
For PLDs, it's pretty simple. For ST, Shield Lob>(FoF)FB>(Spirits Within)SB>(CoS)>RoH and then you just RoH spam and use SW and CoS on CD. For AoE, Shield Lob>(CoS)Flash spam (since FoF doesn't buff Flash's enmity; FoF is a damage buff and Flash is based off attack power).
I'll mirror what everyone else has been saying about Provoke: you should never be pulling with it unless you explicitly *need* the extended range (like when you're pulling the succs away from their groups in AK). It doesn't generate enmity; it sets your enmity at a value based upon the current highest enmity. Starting a pull with it doesn't do anything but start combat, which you can do without burning a resource by facepulling or more effectively by just using Tomahawk/Shield Lob.