Best Cleric spells to prepare?

[Hiro]

As a 5th level cleric that is. With access to domains: Protection, Dragon and Air.

[Emperor Tippy]

What do you want to do? What's the campaign like? What's your party make up?

Just as one example, if you are playing a seafaring campaign then you probably want Water Breathing or Water Walking prepared but if you are in the Underdark then those spells are almost certainly wasted.

[Hiro]

Hellscape game.

water breathing/walking can be useful on some layers of the abyss.

[FearlessGnome]

Protection from Evil.[/Captain Obvious]
Protection from Energy.
A lot of things will depend on where you are. Some layers have really unfriendly environments.
Detect Evil, if your DM does not rule that the background Evil obscures the auras of lesser demons and devils.
Nondetection, if you need to pretend you are not of your current alignment.

[eggs]

The ones the Cleric's going to want to cast.

(Yeah, that's vague. That's what knowledge skills, scouts, divinations and character knowledge are for. Also, depends on build and party composition.)

[navar100]

Bless

I have lost count the number of times a party member only hit the opponent because I had cast Bless. A few times players even made their Will save vs. fear because of Bless. Bless is "only" a +1, but that +1 absolutely makes all the difference.

Protection From Evil

+2 AC and +2 to saving throws helps a lot. Suppressing mind control and hedging out summoned creatures is gravy.

Dispel Magic

When you really need it, you'll be so glad you have it.

Bull Strength

Your warrior party members will luv you. Also good for yourself if you like to engage in combat.

[ericgrau]

In general: prayer, water walk (prepare when needed), inflict serious wounds, bull's strength, spiritual weapon, shield other, silence, augury, bless, obscuring mist
Spell compendium adds: mass aid, mass conviction, holy storm, knight's move (melee clerics), mass resist energy (prepare when needed), mass resurgence, close wounds, omen of peril

Get lots of scrolls of remove X to bandaid every problem that might appear. Including the other half of the fix-its that don't have "remove" in the name.

Here's why prayer is good: A +1 to one guy is no big deal. A +1 or -1 to ten guys is a really big deal. Out of spell compendium close wounds is the all star; never underestimate extra actions. Most of the spell compendium spells listed are pretty outstanding, especially compared to the core spells.

Sanctuary and gaseous form are ok to fill domain slots. Maybe resist energy or protection from energy sometimes.