I taught myself photoshop. It really only takes some time tinkering and a few free tutorials.

Blend modes are an alternative to lowering the opacity. A lot of times just lowering the opacity to make something blend in better looks unprofessional.

Here's an example of what I mean.
If you select a different mode, it blends differently, giving you more options. I took a picture of an African Wild Dog I took at the zoo and put it on a background I played with. The background itself is two different pictures blended together.



And a close up, see where it says linear light?


This is the result.


Here are some other options, and the results.