I've just had my first experience with art theft, fun :/ but I was wondering if there was any really good advice/tips/pointers that anyone could give me? Just in general about art theft, copyright infringement, what to do etc.

:EDIT:
Thanks for all the help guys! It's always useful to look back on and it's good hearing different points of view. If anyone else has something to add feel free! I'm going to try to get some credit for my work at the very least, then move onwards and upwards! I'm hoping to open up commissions in the next week or so, and upload a stack of art that has mounted up over the last couple of weeks/months.