Well, what are you having difficulty with?

Well, break down the image into something more simple. Here is an example of what I'm talking about with animating. In isometrics animating a figure can be a little tricky, so I decided to use a technique I found someone else used. They had a character animation I thought was amazing they, I think,started as a stick figure animation. Then they added the details. This is my own little animation duplicating the idea.

Try to think in phases towards your final goal because your brain has all of these questions about the details of thing you're working on ,but it doesn't have any order to those details. You have to start with something simple then build off of it. Another example is a grass tile. You go and fill in the size of tile and then add on the light based lights and darks.

Oh, and as you asked here are a few tutorials.

http://kiwinuptuo.deviantart.com/art/ Pixel-Art-Tutorial-Basics-196016837

http://kiwinuptuo.deviantart.com/art/ Pixel-Art-Tutorial-Textures-203459613

http://kiwinuptuo.deviantart.com/art/ Pixel-Art-Tutorial-Colors-184802567

http://www.andysowards.com/blog/2012/ 80-epic-pixel-art-tutorials/

It might also help to look up design concepts, or terms. A book to reference would be Principles of Form and Design by Wucius Wong. Just Amazon that and books like that and you might be able to get a better grasp of what you're doing.

And don't be afraid to post your graphical items here and on http://www.pixeljoint.com
I'm certain they'll set you straight on a lot of your missing details.