Protip comes from Gamepro. Gamepro was an American multiplatform video game magazine media company that published online and print content covering the video game industry, video game hardware and video game software. They became most widely famous for its ProTips, small pieces of gameplay tips and advice depicted with game screenshot captions. (The ironic usage is connected to a ProTip provided for the original DOOM: "To defeat the Cyberdemon, shoot at it until it dies"--which is the same method used for every other monster in DOOM.)
Despite the demise of the term in Gamepro itself, the term "ProTip" has been revived as a pop culture meme used to expressing some ironical advice with extreme sarcasm, such as in, "ProTip: Don't call the cops to report your stolen weed."
Randall often delivers other such types of protips in his comics, without calling them that. See the tips category for these other types of tips.
Below is the list of comics where Randall has supplied the readers with these "useful" protips:
Pages in category "Protip"
The following 18 pages are in this category, out of 18 total.