The Chattering Horde: Painting Skaven Stormvermin.

"They are finished my lord", said his aide de camp, as the Archlector turned and passed his gauntlets to another underling. Indeed, he himself had come to that conclusion some minutes ago on seeing most of the Skaven left flank turn and run before sheets of searing flame. That new boy the College of Magic had sent was proving to be capable beyond his years, his proficiency demonstrated by the cleansing blaze that had sent the vermin scurrying (accompanied by an unpleasant smell of burnt hair). His magical power spent, the wizard was now in his tent, exhausted.

A whinnying and a spray of dirt announced the arrival of a messenger on horseback. "Report!" growled the Archlector. "Reinforcements on the left flank, sire"
"Numbers?"
"Some thousands my lord."
A lieutenant-general saw an immediate opportunity to offer an opinion: "Surely of no consequence sir? The enemy have lost tens of thousands on that fl..."
The archlector (alone in his party in having fought the rat-men before) cut him off in mid sentence. He looked up at the rider once more, his forehead creased with concern. "Composition?"
"Heavy infantry my lord. Well armored and..." there was the briefest of pauses.
"...unusually disciplined".
Knowing there to be only one type of enemy troop that could match that description, the archlector immediately turned once more to his commanders, steel in his voice.
"Reinforce the left flank immediately! What troops do we have available?"
"Some levies, light troops from Osterland, a brigade of sword and some outriders sir"
"Send them all..."
"Immediately Sir!" the aide ran away.

"...and let us pray they are enough."

Here is a guide to painting Skaven Stormvermin to a "Tabletop" gaming standard. You certainly won't win any prizes for this, but you will have a unit that looks pretty good on the gaming table. (imho).
NOTE: I painted these some weeks ago, so the colours and amounts used are rough, but they should give you a good idea of how I painted the unit! Painting a test model first is a good idea.
EDIT: Following the launch of the latest Citadel Paint range in 2012, please note that the colours listed below are from the previous range. I hope to have time to rewrite in the future, but for the time being, you can use the conversion chart/ list I made here or use the official Citadel Conversion chart here.

Paints used: Chaos Black Spray, Skull White, Snakebite Leather, Mordian Blue, Codex Grey, Fortress Grey, Calthan Brown, Shining Gold, Tallarn Flesh, Dwarf Flesh, Elf Flesh, Boltgun Metal, Chainmail, Mithril Silver, Blood Red, Bleached Bone.

Step 1: Preparation.
1. Remove the model from its sprue.
2. Carefully file or trim any excess flash from the model. (If the latter, use caution!)
3. Glue model to base.

Step 2: First Basing.
I like to get the application of materials to my base done at this point to save trouble later. Doing it now allows you to correct any troublesome issues with sand or glue without worrying about any painting you might have done.
1. Sand or trim any flash from around the edge of the base. (It really show sup when you paint it...)
2. Paint watered down PVA glue onto the base, carefully avoiding getting excess glue onto feet or shoes, claws, paws etc. (the model's - not yours)
3. Sprinkle a few pieces of crushed coral onto the base. (Obtained at the aquatic section of any pet shop) I find that 2-3 is enough.
4. Sprinkle sand over the base, so all remaining areas are covered.
5. Allow to dry.
TIP: If you have sand that has flowed over the top of the base and onto the sides, scrape or rub it off now. This will allow for smoother painting of the edges later and will look better and tidier in the end.

Step 3: Priming/ Undercoat.

Prime the whole model. I use Citadel Chaos Black Spray. Black is ideal for a model that will overall be darker in tone (and more forgiving for beginners - if you miss painting anything in hard to reach places it just looks like shadow.)
TIP: Make sure you also prime the edges of the base at this stage. This will make it easier for you to paint them later. It is easy to miss the edges and that will mean you need to use more layers of Snakebite Leather to cover the bare plastic (or undercoat all the edges Chaos Black later.)

Step 4: Second Basing.
Personally, I like to get the bases done a bit further at this stage by wetbrushing/ drybrushing the sand. This is because after reaching a satisfied high upon finishing the detail on the bodies themselves then doing lots of bases right at the end is a bit boring. Most people (I think) wetbrush/ drybrush the bases as the final step.
It is up to you!

1. Wetbrush/ Drybrush Calthan Brown evenly over the sand.
2. Wetbrush/ Drybrush Snakebite Leather lightly.
3. Drybrush Codex Grey or Fortress Grey.
4. Paint edges of base with Snakebite Leather.

Step 5: Basecoats.

In this step you will add the basic colours to the model. It is better to use multiple thin coats than one thick coat.

Boltgun Metal: Weapons
Chainmail: Overbrush this onto the chainmail areas, so black is left in the recesses.
Tallarn Flesh: Skin, tail, ears, etc.
Mordian Blue: Cloth or armour.
Snakebite Leather: Straps on vambraces and on the back of the armour.
Shining Gold: Chains, earrings etc.
Calthan Brown: Weapon hafts.
Bleached Bone: Skull on unit banner

Step 6: First Layers/ Highlights.

A layer of lighter blue on the robes.

Highlights of Ice Blue through to a lighter blue on the edges of the armour

In this step we build up the colours ("Layering") in progressively lighter shades on raised areas to achieve greater variation between light and shadow. This could be lighter but separate colours (Tallarn Flesh> Dwarf Flesh>Elf Flesh) OR by adding Skull White in ever-increasing amounts to a single colour.

Most of the time, I do highlights after washes, but with this unit, I wanted to do a layer first and then use washes to see how it turned out before doing some more layers and drybrushing. (I think either looks fine.)

Mordian Blue/ Ice Blue: (2:1) Raised folds of cloth/ (armour on champion above)
Codex Grey/ Fortress Grey: (2:1)

Step 7: Washes.

This step adds shadow and depth to what currently looks like a very "flat" model.

Devlan Mud: Weapons, robes, breastplates/ armour (everywhere except skin)
Ogryn Flesh: Skin, tail, feet etc.
Gryphonne Sepia: Skull on unit banner.

Step 8: Second Layers + Drybrushing.

Having done a first set of layers and then washes, I now did a second set of layers to create more differentiation between the deep shadows created by the washes and raised areas of the model.

Ice Blue, then Ice Blue/ Skull White mix: (1:2) Raised folds of cloth/ (armour on champion above)

Dwarf Bronze/ Shining Gold mix (1:1): Earrings etc.

Codex Grey/ Fortress Grey: (2:1)

Dwarf Flesh/ Elf Flesh mix: (1:1) Skin, leaving some of the previous darker shade.

Bleached Bone/ Skull White: Teeth, nails etc.

Snakebite Leather/ Skull White mix: (2:1) Belt edges, leather straps on armour etc.

Blood Red: Eyes.

Mechrite Red/ Blood Red: (1:1) Tassel on weapon (Champion)

Then, use an even lighter shade of the colours you used in layering the model, and carefully "Drybrush" raised areas. This adds a final natural-looking highlight.

TIP: When drybrushing, first remove almost all of the paint on your brush first by dragging it along a tissue or piece of kitchen towel, otherwise you will get "smears" of paint rather than just leave a fine dusting on raised areas.

Codex Grey/ Fortress Grey: (1:2) Cloth/ robes.
Mithril Silver or Chainmail: edges of weapons.
Ice Blue/ Skull White mix: (1:2) Raised folds of cloth (or edges of armour on the unit champion)
Elf Flesh: Skin, feet, tail etc.
Blood Red: Tassel on weapon (Champion)

Option: Edge Highlights. Using a light colour, paint a thin line along any straight edges that would have a natural shine or that you want to stand out. (e.g. Mithril Silver on weapons or armour. See image below.)

Step 9: Final Basing.

After basing. (Note edge highlights on weapon, armour)

You can see the Snakebite Leather highlights more clearly.
(Belt edges)

Adding some grass or other details to the bases makes a huge difference to the final look of the unit (much more than I first appreciated) and it is one of the simplest things you can do.