Here's a mini-tutorial. I'm also going to show you why you're a dumbass if you post evidence of your crimes online.
I am withholding the blog I got the example image from so she won't DELETE FUCKING EVERYTHING. This woman calls herself a "darling lil' criminal" and has allegedly stolen at least $5,661 since April 2015.
Using Tumblr, I copied the image URL into the first box on
http://regex.info/exif.cgi and pressed "View Image At Url". What comes up is a fair chunk of information:
I know when you took the image, what camera model you took the image,
aaaaaaaaaand
THE SERIAL NUMBER! So, if I were an investigator, I now have more than enough information to establish probable cause, subpoena Tumblr for the user's IP address, subpoena the ISP for the IP's registered user, and obtain a warrant to obtain the camera and shoplifted items. A prosecutor sees the serial number matches up with what you posted, and that's something that establishes your guilt whether or not you threw it all away in a panic.
Getting the EXIF took me all of five minutes.
Some users on /pt/ even found people's names and GPS locations.
YOU ARE AN IDIOT IF YOU POST EVIDENCE OF SHOPLIFTING TO TUMBLR.