it sometimes happens when i have been jacking off for a while and i am so horny that i just can't hold it anymore. my penis is straight up and trembling - if i touched it i'd come all the way, so i just sit there, watch my penis tremble and slowly feel it cumming. sometimes it's just a few drops, sometimes it's already a little shoot. still being on climax i enjoy eating my precum and it sure tastes fine. you can see some pictures and even a video of me precumming on my personal website (link is below).