Just remember that not every meme you make will be as popular as you want it to be and the opposite will also absolutely happen. Commenting a lot will also get you popular but remember to stay away from the politics stream. On imgflip, popularity is very random so try to do quantity over quality. In my opinion, the best way to make your memes popular on the fun stream is to caption a front page meme. But if you want to make your meme REALLY popular, you gotta make something insanely fresh, original, and most of all, original. Thinking about them in the shower will help. If you follow these rules and post at least 2 memes a day to the fun stream, you could be a great imgflipper
