when I am having problems I build a virtual film set using a software program called sketch up. You dont need to build complicated sets in it. You lots of cubes to make the buidlings, you can even turn on shadows, and set the time of day.
heres a link to basic operation.
What I do is make a model, and move the camera to a position that I like and is dynamic. I use this framework to help plan and create a model. this is a thumbnail just blocking out the camera position so that it looks dynamic. I then go to photoshop and just use a couple of colours to block out forms. Once this is done I do a more detailed thumbnail with the comp I like.
Then the moment comes when you start doing your foundation work and create the matte, this is the most important part of the process. My sketches are not pretty, they get better the further you go down the process.
You get to learn perspective, and create compositions which are dynamic. Sketchup is also free, there is a pro version but you dont need to pay out for that just yet.
A couple of quick tips,
never ever place your horizon line dead centre
symmetry kills a composition
look up rule of thirds.
There is tons of stuff out there to help you, plus there is quite a few of us on here that can help out.
Looking forward to more of your work