Most of the fine tune handling of you photos happens at home, in your computer. This is the place where you look at all the pictures, without the emotional attachment of the moment and decide with a clear head which composition is worthwhile your further time investment. If you camera type and memory allows you to take raw files instead of jpegs, you would be amazed about the big amount of settings you could retouch from your computer, on how much you could save a photo that you had no idea it had potential when you took it.
The magic of the contrast slider, exposure button, temperature filters, vignette, different effects and techniques will add value to your work done on the field. The internet is full of tutorials on how to achieve this feeling for your light captures, grudge textures, antique objects.
If you will decide to take on the next step in the post processing level, there is a holy grail for this part of the job too. A graphic tablet will enable you to do major changes, make advanced level compositions from pictures you took at different locations, or correct those tiny details, just as a piece of garbage that you don`t want to see in your artistic interpretation. Not to mention that you can also do the other way around – add up objects, lights, colors that did not exist in the original picture imported from your camera.
Even if you want to try and mix double exposures to achieve that shot that is impossible to take at the location, the computer, a good software and a graphic tablet with a pen would do the magic trick. If you have a graphic designer friend, you can get valuable input and find out the short-cuts, tips and tricks regarding which software is best to use, or which tools do a better job.