How do you add fire on a model/skin?

[carpe_noctem]

How do you add fire and stuff onto a model/skin? Like make it so that there is fire, energy, ice, etc. around a guys hands or something? Or make it look like they are burning? Do you have to modify the model/skin? Or is it triggers?

 

[oz02]

That's done by adding particle emitters in modelling.