There are a number of tricky parts to learning German, but I'm particularly concerned about word order.  I'm using Duolingo to learn and I often miss questions where this is the only thing I get wrong.

Here are a few of my questions/issues:

 - What are the rules for active/infinitive verb placement?
 - How does the kind of sentence change the word order? (i.e. question vs. command)
 - Are there exceptions to these rules?

Unless all of these questions can be answered concisely here to the point where it can be easily understood (not likely), the point of this question is to ask for resources, references, games, or exercises with which to master German word order.  I need a way to practice this specifically without stabbing in the dark like I do with Duolingo.

Criteria:

 - Provides explanations for all or almost every exercise
 - Specifically targets the issue of word order
 - A progress tracker would be nice, especially if it's like Duolingo's point system
 - Free would be quite nice

I imagine that a kind of drag and drop words game would be most along the lines of what I'm looking for, especially if it provided explanations for why answers are correct/incorrect.  However, I'm open to other suggestions as well.