Aid

Enchantment (Compulsion) [Mind-Affecting]
Level: Clr 2, Good 2, Luck 2
Components: V, S, DF
Casting Time: 1 standard action
Range: Touch
Target: Living creature touched
Duration: 1 min./level
Saving Throw: None
Spell Resistance: Yes (harmless)
Description

Other Information
Bonus on attack rolls and saves against fear, and a small amount of temporary hit points.

Pros:

Multiple bonuses: Attack bonus and temporary hit points are always useful, the bonus to saves against fear is occasionally handy.

Long enough duration to cast before entering a situation where the bonuses will be needed.

Cons:

Bonus to saves against fear will be unnecessary most of the time.

Tricks/Combos:

The temporary hit points can be used as a roleplaying device when cast on a dying creature. A "healed" creature could be questioned and then released, only to die a few minutes later. Or it could be viewed as a curse, or a "countdown to death" such as those often seen in video games, if you're really sadistic.

Overall:
A decent buff spell to use on any character who will be making attack rolls, but especially primary melee characters who will need the temporary hit points. If you know beforehand you will be facing something with a fear effect, Aid goes from a decent spell to a good spell. Once again, primary melee characters benefit the most, since they likely have low Will saves to begin with. Also versatile as a last resort temporary healing spell.

Recommended for Clerics?
Yes. Always a good choice if going up against opponents with a fear effects, but even if not, still a dependable buff spell or backup healing spell. Mostly a good choice because by memorizing a single spell you can fulfill various needs.

Recommended as a scroll?
No. Although this spell has multiple effects, there are other, lower-level spells that will accomplish a single effect more effectively. Bless (1st) will give all of your allies the +1 on attack rolls, Resistance (0th) will grant a +1 bonus on all saves, and Cure Light Wounds (1st) will heal about the same hit points, but for good, not temporarily. Aid is worth memorizing because your spells per day are limited. Your scroll choices are not, so it's better to just carry a few different, less-expensive scrolls that can accomplish the same as a scroll of Aid.

Acid Splash

Conjuration (Creation) [Acid]
Level: Sor/Wiz 0
Components: V, S
Casting Time: 1 standard action
Range: Close (25 ft. + 5 ft./2 levels)
Effect: One missile of acid
Duration: Instantaneous
Saving Throw: None
Spell Resistance: No
Description

Pros:

Ranged touch, No save, No SR

Overall:
One of the few cantrips that will deal damage. More useful in provoking/intimidating someone or testing resistances than actually dealing damage.

Recommended for Sorcerers?
No. You get only a handful of 0th level spells. Ghost Sound, Dancing Lights, Mending, Open/Close, Prestidigitation, Message, Detect Magic, Mage Hand - these are all more useful choices. You should have plenty of Magic Missile spells to deal damage.

Recommended for Wizards as an initial spell choice?
Automatic. Usually not worth memorizing, though no SR means it is better than the other damaging cantrip Ray of Frost.

Recommended as a scroll?
No. Don't bother.

Acid Fog

Conjuration (Creation) [Acid]
Level: Sor/Wiz 6, Water 7
Components: V, S, M/DF
Casting Time: 1 standard action
Range: Medium (100 ft. + 10 ft./level)
Effect: Fog spreads in 20-ft. radius, 20 ft. high
Duration: 1 round/level
Saving Throw: None
Spell Resistance: No
Description

Other Information
Area of effect spell. Deals 2d6 acid damage to each creature and object within the fog on caster's turn. Minimum level for 6th level spells is 11th, so that's a minimum of 11 rounds.

Obscures all sight, including darkvision, beyond 5 feet. A creature within 5 feet has concealment (attacks have a 20% miss chance). Creatures farther away have total concealment (50% miss chance, and the attacker can’t use sight to locate the target).

Any creature attempting to move through the fog progresses at a speed of 5 feet and it takes a -2 penalty on all melee attack and damage rolls. Prevents effective ranged weapon attacks except for magic rays and the like. A creature or object that falls into Acid Fog is slowed - each 10 feet of fog that it passes through reduces falling damage by 1d6. A creature can't take a 5-foot step while in Acid Fog.

Pros:

Large area, No save, No SR.

Repeating effects in multiple rounds with no further effort required.

Can force spellcasters to make ongoing Concentration checks.

Limits vision, grants concealment.

Slows creatures.

Penalty to melee attacks, prevents non-magical ranged attacks.

Acid damage can affect large quantities of items at once.

Cons:

Doesn't function underwater.

Can be escaped via extradimensional travel (Dimension Door, Teleport, etc.)

The falling damage negation from Solid Fog is virtually useless.

Tricks/Combos:

Combine with Dimensional Anchor to prevent opponents from magically escaping the fog.

Combine with movement-hindering spells like Grease or Web to prevent opponents from leaving the fog. Or use a bull rush or similar methods to push someone into the fog.

Use in an enclosed space for maximum damage (think execution gas chamber.)

Area of Effect immunity: if you have acid-immune allies in melee with opponents, you can cast this spell on top of them. Opponents will be forced to fight and endure the acid damage, or slowly retreat and allow your allies to pursue them.

Since it deals damage to each object with no save/SR, it can quickly destroy large amounts of items, including magical ones.

Cast multiple Acid Fog spells next to each other to make it even harder to escape the fog.

The acid damage can be used to eat through walls, ceilings or floors.

Widen Spell: doubling Acid Fog's area makes it twice as hard to escape and thus twice as dangerous. However, the +3 spell level is harsh. Chances are you are better off using a 9th level slot on something else.

Extend Spell: doubling Acid Fog's duration makes it deal twice as much damage to something trapped inside. A good investment for +1 spell level.

Overall:
An extremely useful, versatile spell that is effective in all but underwater scenarios. Being able to virtually negate an opponent's movement (or a group of opponents, for that matter) is nice. Being able to do so with no save is great. Being able to do so with no SR is better. Being able to do so while dealing continual damage is even better. Being able to do so while also damaging all of the opponent's equipment is just evil.

It can also be used to stop pursuit. Placing 8 rounds of acidic, solid fog between you and your pursuers tends to change their minds rather quickly. It's no longer useful as a 20 foot cushion for negating falls (the acid damage is just as bad) but that's a very minor loss.

The acid damage is not overly dangerous for the lethal damage it inflicts, but its ability to affect equipment and other items is extremely powerful. You can destroy an entire area of unattended objects - 2d6 acid damage per round for a minimum of 11 rounds will decimate all but the strongest of objects. Attended objects/equipment in an Acid Fog stand a good chance of being destroyed even if their bearers escape as quickly as possible.

Recommended for Sorcerers?
Yes. Even if you already have Solid Fog, the item damage ability makes Acid Fog an worthwhile pick. If you have both Solid Fog and Acid Fog and your opponents have no equipment or items to destroy (such as an animal), you are better off using Solid Fog and using your 6th level spell slot for something else.

Recommended for Wizards as initial spell choice?
Yes. Even if you already have Solid Fog, the item damage ability makes Acid Fog an worthwhile pick. If you have both Solid Fog and Acid Fog and you know your opponents will have no equipment or items to destroy (such as an animal), you are better off memorizing Solid Fog and using your 6th level spell slot for something else.

Recommended as a scroll?
Yes. You should always have Acid Fog available to cast.

Acid Arrow

Conjuration (Creation) [Acid]
Sor/Wiz 2
Components: V, S, M, F
Casting Time: 1 standard action
Range: Long (400 ft. + 40 ft./level)
Effect: One arrow of acid
Duration: 1 round + 1 round per three levels
Saving Throw: None
Spell Resistance: No
Description

Other Information
Used to be known as Melf's Acid Arrow. 2d4 acid damage per round (average 5) with an additional 2d4 for additional rounds. By the time you can cast this, it's automatically lasts at least 2 rounds, which means an automatic 4 damage. The maximum number of extra rounds is 6, at 18th level.

Pros:

Ranged touch, No save, No SR.

Repeating effects in multiple rounds with no further effort required.

Can force spellcasters to make ongoing Concentration checks.

An early source of acid damage.

Repeating damage forces spellcasters to make concentration checks.

Cons:

The repeating damage is not very high; any smart caster will have enough ranks in Concentration that this will be a minor inconvenience at best.

For overall damage, a Scorching Ray will almost always be more effective.

Tricks/Combos:

At higher levels, the increased duration and long range can make for a simple hit-and-run attack.

The repeating damage stacks with multiple castings.

Could be used to set "delayed" effects (using the repeating damage to gradually eat through an object after you've already left.)

Extend Spell: +1 spell level for double the damage is a good investment.

Overall:
Not a terrible spell, but not a great one either. It's handy in certain situations, but Flaming Sphere, Invisibility, Levitate, Scorching Ray and Shatter are all more effective, more versatile choices. The no SR is nice, but if you are against something with SR that you cannot beat, chances are you're doomed if all you have to hurt them with is Acid Arrow.

Recommended for Sorcerers?
No.

Recommended for Wizards as an initial spell choice?
No. It's worth buying a scroll to scribe it into your spellbook, though.

Recommended as a scroll?
Yes. It's a no save, no SR damage spell, which can always come in handy. The acid damage is a bonus. Certain enemies will find the repeating damage a real pain in the ass.