Your eyes? May sound stupid but if an image doesn't look right  to you it's not right. You can use tools for it, but that is someone else's predetermined way of how things should look. In the end you decide if you like the result and outcome or not. Use tools.... but also depend on your eyes and personal taste.

Artwork and 3DToons items, create the perfect place for you toon and other figures!

http://www.renderosity.com/mod/bcs/index.php?vendor=23722

Due to the childish TOS changes, I'm not allowed to link to my other products outside of Rendo anymore :(

Food for thought.....
https://www.youtube.com/watch?v=pYZw0dfLmLk