Target Marking Tips For Tanks

[Maelwys]

I'll echo the "Don't use X" comment above.
It can get confusing especially if there's a language barrier between teammates. "Attack1" should be universally understood.

You're a Tank. You basically need to tell the DD's what target they should be focussing on.
This is NOT THE SAME as the target you're currently attacking, since you should be alternating targets regularly in order to keep solid hate on multiple foes.

If you're lazy and/or play using a controller and have problems juggling a lot of macro commands, then all you need is a "/mk attack1 <t>" macro.
Whenever you're about to engage a group of foes, target whichever foe you want the DDs to focus on and press the macro.
Once that first foe is about to die, target the NEXT foe you want the DDs to focus on, and use the macro again.

That one marking macro should get you through the vast majority of the game without any problems or whinging from teammates

If you want to raise the bar a little bit, you can set up a few more macros to help your teammates out more. Example:
"/mk attack2 <t>" (so you can mark the ORDER in which you want DDs to take out the first two targets. Once Target #1 dies, you can re-mark #2 as #1 and pick another foe to mark as #2)
"/mk bind1 <t>" (set this on a foe that you want the WHM/BLM to keep slept. Some mages will mark their own mobs, others will not bother marking them and cast sleep randomly, occasionally some will wait for "instructions".)
"/mk ignore1 <t>" (set this on a foe that you want the DDs to specifically ignore - example: dungeon boss fight phase whenever you want DDs to concentrate entirely on the spawning ads, etc.)

Save those marking commands to Macros, and pick and bind a key to trigger for each one.
It might help to also setup macros to target any previously-marked foes, and bind those same keys to trigger those targetting macros whenever a modifier (Shift, Alt, Control, etc) is held down.

I use a PS3-style controller and a keyboard. I've got character movement bound to the Controller's Left Analogue stick, which leaves the normal 4-way Directional-Pad free.
I've bound the D-Pad Up/Right/Down/Left axis to macros that mark my current target (or my mouseover target if I don't have anything currently targetted) with Attack1/Attack2/Bind1/Ignore1.
Holding down a Trigger button (in my case Shoulder Button L1 which is bound to "Control") alters the D-Pad Up/Right/Down/Left binds - they now make me retarget whatever I've already marked with Attack1/Attack2/Bind1/Ignore1.
You could do something similar with the Numpad or Function Keys and expand it if needed for the remaining mark types.