One think I know that integrates picture and helps a bit with realism is as follows:
Copy image to new layer
add difusse glow filter on top, with parameters as to add quite vissible glow with little grain, but not too much of both (say, parameters 4, 4, and 8 in cs2)
set transparency of this new filtered layer to 40 - 50
this will probably result in less contrasted and lighter image, so last thing I do is rise contrast and lower brightness of the orginal first layer
All together it adds subtle glow to lighter areas, and sort of melts objects together colourwise (very subtle) so it looks a bit less like separated objects put together in a scene and more like an integrated whole. Any tips and strategies you use, guys?
here is example, before and after (this work was suposed to be over exposed with light):