Gathering up some ideas, tips and advices.
Thanks to Agash for the idea and whole shaman community for the information provided!

First of all, read this guide. It's out of date from some parts of it, but basic numbers haven't changed anywhere.
http://elitistjerks.com/f47/t20765-shaman_enhancement/

----------------------------------------

This post will be split into four sections:

1. Talent Specs
2. Gearing
3. Glyphs
4. Spell Rotations (not actually rotation, but priority list!)

==================================================

1. Talent Specs

This has been discussed multiple times and for now it seems that with small modifications due everyone's play style, gearing and personal favors:

When mana is a problem (gearing phase before T7):
http://www.wowhead.com/?talent#hVbhqZhbxIoxdIhusRuVo

High End raiding:
http://www.wowhead.com/?talent#hVhhqZhbxI0xdIhusRuVo This is what I'm most likely going to use.
http://www.wowhead.com/?talent#hVbNVZhLxc0xdIhuskuVo This is very handy when you're at interrupt duty ( There is LOADS of those fights in Ulduar!!)
http://www.wowhead.com/?talent#hVbIVZhbxf0xdIhusRuVo Something worth to try also.

All talent builds has their Pro's and cons.
In the end, It's up to you what talents you want to prioritize over other.
Remember this: The best specc is only the one which you enjoy playing the most!

Someone can't live without instant Ghost Wolf and another (this is me:) is just too lazy to drink in every turn and therefore speccs for maximized manaefficiency. You can find many discussions about different speccs and talents later on in this thread, so just pick what suites you the best.

==================================================

2. Gearing

Base stats:

- Stamina: Every point of stamina provides 10hp for shaman.
- Strenght: Shaman will receive 1Attack Power(AP) from every 1 point of STR
- Agility: Shaman will receive 1Attack Power(AP) from every 1 point of AGI plus 1%melee crit from every 83.33 Agility.
- Intellect: Shaman will get 15mana from every 1point of INT. With Mental Dexterity talent, you will also gain 1 AP / 1INT. On top of that, you will gain also 1%spell crit from every 167int. Ancestral knowledge boosts intellect even more, depending how many points you have in that talent.
- Spirit: Spirit regens your health and mana over time. This is totally worthless for shamans.

Summing it up in priority order:
1. Agility : 1AP + melee crit (and armor)
2. Intellect: 1AP + Spell Crit, 15mana/1INT
3. Strenght : 1 AP
4. Stamina: 10Health/1STA
5. Spirit: Worthless junk

Even when STR is higher in the list than Stamina, you should consider wether you like to have more health and thereby help healers job, or flat 1AP gain from 1 STR.
Personally I would choose STA over STR if items have same stats otherwise.
In either case, you should never enchant or gem in order to get more STR.

Special stats:

First of all, there is some VERY IMPORTANT stats which you should get capped.
Hitrating is the most important stat to get capped due the fact that huge part of our dps comes from spells.
When you have capped hit, aim for capping expertise.
After that, you should try to find good balance between Attack power and Crit.

3.1 Patch also brought Armor Penetration and Haste back in game.
All classes benefit now 25% more from armor penetration and enhancement shamans now receive 30% more melee haste from Haste Rating. Both of these stats are beneficial only if you have really put some effort in gathering them. It haven't been decided yet wether it's good or bad to get these stats.

Base stats which you should reach:

Hit cap for specials (Stormstrike & Windfury Weapon) :
- 9% hit required.
- We get 6% from Dual Wield specialisation so you need 3% from gear.
- At level 80 thats 99 hit rating to cap specials.

After that, you need to cap your spell hit which is 17% (16% for alliance).
- In a raid you can expect to get a 3% hit buff from moonkin druids or shadow priests.
- This leaves 14% from gear (13%) --> 367(342) hit rating at 80lvl.

----------------------------------------

Expertise:
- 26 Expertise (6.5%) means your attacks cannot be dodged or parried.
- You will receive 1 expertise from every 8.19 expertise rating
- At level 80, that means I need 214 Expertise rating.
- You will get 9 expertise from Unleashed Rage -talent 26-9=17
- When talented right, you need to gather 17*8.1975 = 140rating

Previous thinking was that expertise only worked in "chunks", that values are rounded down to whole integers. This has recently been disproved and expertise, despite what the UI might lead you to believe, does not drop fractional points. That is, if you have rating sufficient to give you 25.5 expertise rating, you actually benefit from all 25.5 points of it, not only 25 as has previously been conjectured.

----------------------------------------

So, summing them up;
- Soft hit rating cap: 99 Rating / 9%
- Expertise: 140 Rating / 26 Expertise (6.5%)
- Spell Hit rating cap: 367 Rating / 14%
- (You should also aim to 25-30% spell crit just to make sure that you'll get all proccs rolling)

----------------------------------------

After you have capped these stats, you should start gemming and enchanting for either Attack power, Haste or Agility. (best way to find out what you need is to sim it =)

----------------------------------------

Crit rating:
Enhancement shaman is very fortuned in this case.
Nowdays crit rating benefits both, melee AND spell crit.
I haven't intentionally put that much effort in to this because your gear should provide you enough crits,
so that you'll reach atleast 80% (the more the better!) uptime for Elemental Devastation and Unleashed Rage.

----------------------------------------

Haste:
Previously this was more or less wasted point in itemization, but now we need to take this in consideration, because after 3.1. enhancement shamans benefit 30% more melee haste from haste rating. They also lowered our meleehaste gained from flurry effect.
Windfury has hidden 3sec cooldown, so getting your weapon speed as near 1.5 as possible by gathering haste, could be ideal (not sure how wise it is anyways comparing to other stats..)
Maelstrom Weapon is PPM (Proccs per minute) based talent, which proccs better with slow weapons.
When you stack haste, you swing faster with slow weapons, you will get more proccs from MW.
Also, pretty big difference can be obtained from lowering the Global Cooldown by stacking haste.

----------------------------------------

Armor penetration (ArP)
As said before, we are getting 25% more from ArP, so this stat should be taken in consideration when speaking end game raiding (when your other stats are in good condition).
Most of our DPS is still coming from melee damage, which can be - and is been reduced by Boss armor migitation.
I guess we will see more items with ArP when progressing in raid content (Icecorwn)

----------------------------------------

Spell power:
At the beginning of WOTLK there was possible to do enhancement in two ways.
The more traditional way was to put almost all talents in "melee" talents and only spicing them up with spell talents.

The other way of gaming was to specc elemental/enhancement hybrid. Itemization was more from elemental side, but you was still playing a melee class. First Blizzard was trying to cut off this playstyle by organizing our talent tree, but still you was able to specc enhancement and by clever usage of itemization, you was able to do immense amount of damage produced mostly from flametongue weapon proccs.
Main idea this style of playing was to imbue both FAST weapons (caster weapon in main hand, fast offhander) by flametongue weapon and you was stacking spellpower.

when 3.1 hit, blizzard normalized flametongue weapon damage: "Flametongue Weapon: Bonus damage from spell power now based on weapon speed. Slower weapons will benefit more from spell power." which was more or less end of this style of playing.

Now you shouldn't put any effort in gathering spellpower.

----------------------------------------

Choosing weapons:
As GhostCrawler has said, enhancement shamans should be dualwielding SLOW weapons in both, main and offhand.
In PvE content, you should imbue your main hand weapon with Windfury and offhander with Flametongue.
Summing it up:
SLOW / SLOW
Windfury / Flametongue

==================================================

3. Glyphs

There is few different variations about the glyphs, but mainly you should be using these:
- Storm Strike
- Lightning Shield
- Flametongue / Feral Spirit

I haven't had a change to try that feral spirit glyph yet, but I'm confident it will be one of the best glyphs we have.
This glyph has one downside though: you really need to start using those spirits to get all out from the glyph. Also at trashes and farming.
With 3 minute cooldown, you really need to know when to use spirits to get the best out form them.
Timing wolves right with trinkets, potions, cooldowns and Blood Lust, can bring you HUGE difference in DPS.

There isn't any spesific minor glyphs for enhancement shamans.

--------------------------------------------------------------------------------
Continues in next post