In EOT or EOD or EOS, in the 'quiz' at the beginning.
This is such a large answer that the this link is easier then copying and pasting the list so here is for EOT and EOD
Each Pokemon you can get has a certain nature and each answer gives you certain points(+timid, stuff like that) so look at my source and you will see witch answer gives points for what nature, also the nature you need to get changes depending the gender you chose.
I will tell you what nature is needed for certain Pokemon soon
nature required for each Pokemon