compositing in green screen for my film

Three is three main elements which I always consider while compositing the green screen.

1. Proportion

2.  Depth

3. Colour correction and grading.

The proportion of the subject and the background should match.  I pick one tree of the photography and blur every thing else and in that way I made the photo from one dimension to 2 dimension. 

i colour correct the subject according to the back ground and graded as same colour so they match more as more sellable.