I love wearing a side ponytail. Depending on how you wear it, you can wear it for formal events such as a wedding or it can be casual for every day. If I just wore a ponytail it would look very casual but for some reason you put it to the side and there is some elegance to your look. I like to put the ponytail on the side my bangs are on - it works for me... But whatever you are comfortable with.
This tutorial shows and great way to style a side ponytail.
Hope you enjoy!