Ret paladin most important stat.

[Indris]

~30% crit is plenty, you also want to be hitcapped or close to it 'cause missing that HoJ or repentance will make you cry blood. Other than that, Str all the way, our attacks scale way too well with it, and you also gain extra spellpower with Str as well sooo no reason to go for anything else really.

[nobu]

Strength>Crit/Hit>Haste>Armor penetration.

[eodem]

Strength>Crit/Hit>Haste>Armor penetration.

PvE:
Strength > Hit (untill capped) > Crit > Agi > Expertise (untill soft capped --> 26) > Haste/Armor Penetration
Expertise avoids having bosses/mobs dodge/parry and increasing their parryhasting. Softcap removes their dodge and increases your damage. Hard cap is not reachable with current ingame DPS gear (removing the parry aswell and giving you the freedom to attack the boss from the front without hurting the tank). It's not that important since you will attack from the back mostly, but it's usefull for those bosses with random target abilities and change facing for it.

I'm not much for a PvPer but here's what I think (!, don't flame if I got it wrong):
Strength > Crit/Hit untill PvP capped (5%) > Agi> Expertise PvP cap > Armor Penetration > Haste
ArmPen is usefull for PvP always and unlike other stats it still scales exponentionally. But for PvP I don't see the use for Haste. Most of our Damage output comes from abilities, not from Whites. It's usefull for PvE to an extend (more white hits = more dmg with seal of Blood/Martyr) but for PvP it does almost nothing.

To close things off... I would always socket for Strength and enchant for Strength/AP/Agi.

[Adamson]

^^

You're still placing too much emphasis on hit. Even at 1/2 your hit cap Str and crit are still better.

As long as you have ~200 hit rating you should never gem or chant for hit.

[Undertaker]

Sorry for the bump, but where does expertise fits in all this? I'm still leveling mind you, but when I can get a load of expertise but at the cost of strength/crits or both, I don't know what to do.

I really need some clarifications, thanks.

Hit (200~ hit) > Strength (until you're around 3000 ap) > Expertise

is how I go at PvE

[eodem]

I actually went into Naxx10/25 with only ~80 hit. So yes Strength is far more important. Hit and other stats will come with gear.

[Trinnium]

Spirit.

Truefax.

[Killacrush]

Strength.

Increase attack power, is affected by Divine Strength, and is multiplied by Kings.

Never realy looked at it that way, soo is kings a better buff then might may i ask ? < going off-topic so for what i think its [ Strength ]

[cryogenic]

str, 200 hit rating for pvp.......... some people should read the topic.

divine str and kings is not all, sheath of light adds to your judgement and consecrate damage this makes strength worth a stupid amount of effective damage compared to the other stats in stacking by both percentages.
seals can't miss making hit less worthwhile for a paladin, and judges can't be dodged parried making expertise and hit both not as valuable as strength, you should still lower your chance to miss or dodged as much as possible one or two items with hit rating should be enough for pvp everyone is likely hit capped for pvp atm with pve gear.
expertise is likely more important then hit rating in places where you fight prot specs.

[Neferium]

you don't need alot of hit in pvp. but it is still needed. After hit get str and crit.

[Maihes]

~5% Hit if possible then as it has been stated STR STR STR.

Seals etc double dipping from AP via Sheath makes it by far better point for point for Str. Unless you NEED the extra Health, Might > Kings (more spell power and AP)

But then again 15/3/53 Ret Pally here ^ ^