I've begun a new hobby. This hobby doesn't have any real set hours or locations. I am "THAT GUY" - also known as "SOME GUY" or "SOME UGLY MIDDLE AGE FAT BALDING GUY." I am here. I am there. I am everywhere. I am unknown. I show up in France. I may be seen in Spain. I may even be remembered in Egypt or on a cruise somewhere. I am.....a PHOTOBOMBER.
Photobombing is where you appear in the background of someone else's photos and....ruin them or at least detract from them by "photobombing" them - usually with a ridiculous face, obscene pose or something that just doesn't go with it. 
My hobby as a photobomber officially began on June 12th at my daughter's dance recital. There were a million parents around taking pictures of their daughters in their outfits and the family reuinions. By carefully placing myself in the background and watching people set up for photos, checking sight lines and such - I could effectively photobomb several families at the same time.
I don't know that there really are any tips for photobombing other than you gotta be willing to do it and can carry it out in such a way that you don't completely distract people who are being photobombed so that you lose the opportunity to do photobombing.
Anyways, for now - this is a new hobby - we'll see what turns up with it.
