Short version:

1 - Pull Titan to the edge of the arena, facing to the outside.
2 - Solidify threat.
3 - Pray your party doesn't suck.

Long Version:

Titan is actually much harder on your healers and DDs than it is for the tank. Tanks have it extremely easy until the Post-Heart phase. You'll literally not get targeted by any attacks unless you're the only man left standing. As a tank, there's only two critical moments you have to worry about, Mountain Buster and Bombs. Most bombs are pretty easy to dodge (get as close to the edge as you can and stay in the center, you'll avoid the blast radius), but one bomb formation (it'll be a circle formation) is very very easy to screw up on and it's usually better to use a CD just take one bomb to the face.

Mountain Buster is the ability you'll have to look out for and he'll only do it after the Heart phase. It'll be the first very ability he does and it can do up to 3.3k in damage without any mitigation. Party members will instantly die to this and only a tank can sustain the damage. Rotate your cooldowns to ensure you'll always mitigate the damage (I used Sentinel > Bulwark > Rampart). Using Flash's blind effect also helps since it'll give you the chance to dodge MB.

Otherwise, the rest relies on your other members, which you have no control over. The hardest part about Titan is getting a good party.