If you want a little more staying power from a prestige class, consider the War Priest prestige class. It costs you (IIRC) at least one level of spellcasting and forces you to cater your feets more toward a combat focus, but you pick up an extra domain and (again, IIRC) a d10 for hit points over the course of its ten levels.
Of course, I don't have Complete Divine handy. You might have to give up a touch more spellcasting than that.
There's a feat in Complete Warrior - Improved Toughness I think is the name of it - that gives you +1 hit points per class level. Taken early in your career, it's like a +2 bonus to Constitution at the expense of a feat. Throughout your career, that's probably enough hit points to survive one additional blow in combat.
Another consideration is stacking things. Exploit the fact that Armor bonus, Shield bonus, and Natural Armor bonus stack. If you play a dwarf, you can wear heavy armor without sacrificing any movement (since they have 20 feet base as it is). An amulet of natural armor + magic suit of full plate + magic shield = high armor class. Dexterity won't be your friend, but the high AC will offset that. Get magic items that provide DR and buff your Consitution and you'll be able to soak damage.
If you can avoid it, don't pick a god, be one of those "ethos" clerics that can pick any two Domains. If you're going to be in combat, consider War and Destruction, but don't overlook things like Fire or, if you think you'll need to be a band-aid, Healing. War will let you use better weapons.
If you're consistently going to be casting in combat, consider Combat Casting or just pouring ranks into Concentration so you can cast defensively with a good amount of success. If undead aren't a real threat in the campaign, you might want to look into the Divine feats in Complete Warrior that will let you channel your turn undead attempts into defensive (or offensive) capabilities.