Tanking in D&D 3.5
Tanking in D&D 3.5 isn't like in massively multiplayer games. Dumb foes like rats and mindless undead will likely attack whatever's closest or whatever attacked them. Smart foes need a very good reason to attack the beefy guy (you) instead of the squishy caster.
In the NFL, the opposing team needs to get through your team's defense (melee guys) to reach the quarterback (casters). Quarterbacks make important decisions that often affect the game's outcome. Some QBs are glory hogs, trying to do everything themselves, and sometimes these are successful. Typically, more successful QBs are team players that try to involve everyone on their team Until foes can regularly teleport and dimension door or otherwise move very quickly, this is typically how things go.
At higher levels, merely standing there and looking tough won't cut it: You need to get in your enemies' faces. You need to be at least as mobile as they are and have at least as much reach. You need high initiative, HP, AC (especially touch AC later on), and saves. To keep up, you must eventually be able to fly and perhaps jaunt or teleport.
Ultimately, you must be a threat. Be as mobile as you want. If you can't stop foes from stopping your allies- such as by stunning your foes, immobilizing them, or cutting them to ribbons before they can act- you aren't doing your job as well as you could.
How can we optimize this?
Certainly, spells are one way, but I'd like to avoid spells cast by this character. (Magic does enough already.) Assume any spell cast by this character is level 2 or less.
What maneuvers, classes, class features, and such do you believe most important? Assume we start at ECL1 with a 28 point buy and all first party material available, but no magazines. Assume this tank has a functional and friendly Rogue, Cleric, and Wizard- 3 separate characters, not some hybrid- of equal ECL to protect.
In no particular order...
-AC: A low AC may invite more foes to target you, but a low touch AC especially means casters can have a field day with you. Ray of stupidity? Optimized orb of force? Ray of clumsiness? Beware!
HP: You must be able to take blow after blow. Once your foes can teleport past you, merely standing there with long reach ain't enough.
Hit Negation: If I see my foe has mirror image or displacement or blur active, I'm much less inclined to aim for him. If, however, you're this guy who's in my face and who I can't shake, I'm stuck attacking you or begging surrender or trying to flee.
-Initiative Boosters: You need not go as soon as the party's Wizard, but Improved Initiative, the Aggressive trait, and Moment of Alacrity go a long way toward reliably acting before the other side.
-Pounce. You need mobility. As a front-liner, if you can only attack something once after moving, you're at a significant disadvantage compared to a pouncer.
-Save Swap Maneuvers: Will and Fortitude especially. Moment of Perfect Mind is level 1 for good reason, though non-casting tank implies a high Fortitude save.
-Uncanny Dodge: Flat-footed people die to sneak attacks more often. Improved Uncanny Dodge is optional.