Hi,
In the resources area of this site is a tutorial on how to create an Isometric Grid in Adobe Illustrator.
In order to help your line work snap to the grid, lock the grid layer and create a new layer for your line work.
Go to 'Menu' _ 'View' and choose 'Smart Guides' (command U).
This will snap your line work as you draw to the grid lines on the grid layer.
This is a great knowledge site for Tech Illustrators. I thought it was time I contributed in my small way.