Kitru's advice about energy management is good, although you won't have energy blast for a while and I imagine shield cycler isn't proccing as much as it would for a geared 50 tank with a high shield chance.
Weave in more hammer shots generally. Take explosive shot off your bars and try to avoid using explosive surge unless it is free or you know you won't need ammo for a while.
Also, pay attention to who is hitting what. Healers don't generate much aggro but something like a gunslinger does. Use your proper rotation on the DPS focus target and sprinkle a few hammer shots on things going for the healers. Sticky grenade loses out to abilities that benefit from spec points later on but even at 50 it's a useful ghetto cc and does enough damage to beat healer aggro.
For bosses or mobs with a lot of health you can afford to waste ammo early on for a big burst of threat and then coast on taunts after that.
Edit: No guide is perfect but I liked this one