This helped me a great deal. https://www.youtube.com/watch?v=iH-o0YNXlIA
Also, if you go onto Amazon you can find isometric grid paper - great for hashing out graphics before you work on them digitally.
Redhades has a good example that helped me when I was doing an isometric game. Here's at least one version of it... can't remember if there's a newer one out there somewhere. https://www.create-games.com/download.asp?id=6517
The most accurate way to do the sorting is for your objects to all have X, Y, and Z coordinates (using alterable values) as well as X, Y, and Z dimensions (also alterable values). This makes sense, since isometric really has 3 dimensions, not 2. You position the objects' 2D X and Y positions on the screen using those X, Y, and Z alterable values. In other words, when you want an object to move, you change the XYZ values a certain way, then set the object's X and Y position on the screen to what it should be based on those values, if that makes sense.
Anyway - you use these values for layering the objects properly. When objects overlap, test the XYZ dimensions against each other, and figure out which object goes in front or behind. Static objects can get sorted once at the beginning of the frame, then you just always check the moving objects against statics and each other. It's a little complex, but it works!
I got a 404 error on the download link.
On my computer now (was on my phone) - attached the file for convenience. This is Redhades' isometric engine. Has a very thorough explanation .doc file in there. Like I said it's a little complex, but it works
Perfect. Thank you for the salvage.