Quiero saber cuando usar cada de estas palabras ....
aun e incluso both means even ,
todavía e aún means still ,
I do not know I want to use these words but I am a little confused
I saw this picture and I want to say ; it is right , the smile worthes even more , "es cierto,la sonrisa vale aun o incluso más ".I mean more than all the money. Which should I use???? 
GRACIAS
2 Answers
I don't believe there is a real rule for which one to use. They are synonyms which means they're interchangeable. You can use whichever one you want. In this case, I would use aun because I think it sounds better, but it's really up to you.
Also, take a look at this post, it may help you.
According to the website, aun and incluso are more or less synonyms when used as adverbs.
However, aun is not listed as a preposition, but is listed as a conjunction.
Incluso, however, is listed as a preposition, but not as a conjunction.