Hi there
Have a look over at the Eldar Army Profile section in the Articles part of Dakka. It's at
http://www.dakkadakka.com/wiki/en/Category:Eldar_Army_Profile
If you can see a style of army you'd like, you could
PM the user and ask how he achieved that effect.
With painting Eldar, there are two main schools of thought - one is to paint all your different aspects in their traditional codex colors (tan for Banshees, green for Scorpions etc), making for a bright and colorful army, but maybe a bit too diverse and not very cohesive throughout the force. Or you can throw the codex 'painting guides' out of the window and create a color scheme that the entire army sticks to, which is what a lot of the people in the Articles section have done.
If you're starting out painting, I'd recommend using lots of sprays and washes. Find an acrylic spray in your army color (you can get them from art shops), spray all the models the correct color (after undercoating with primer) and then use washes and drybrushed highlights to bring out the detail. Then, the only bits of the models you have to paint by hand are the little details, weapons, and different colored sections.
This will allow you to build up your detailing skill and brushwork on little areas of the model, rather that just jumping in and attempting to paint crisp, clear, shaded blue armour by hand on your first go!!
Obviously this method kinda works better if your army has one color scheme, but even if not, it may be a good starting point for your guardians and tanks (which all tend to be in the same Craftworld scheme)
Hope that helps!