Alright first your going to need your supplies and well i'm going to warn you that you may or may not have this luxurious item in your household. All you need is (drum roll please)......your toilet. and tape sorry.
Step 2: Setting up
Ok now all you have to do is go in your bathroom and find your toilet. Now take the lid off of the top of your toilet. Now you will see a tube running along and into a pipe thing standing up inside of your toilet tank. So what you have to do is take that tube out of the pipe thing (don't worry it won't destroy your toilet ) and stick it so that the open part (that was sticking in the pipe) is right at the edge of your toilet tank and it is facing out away from the toilet towards your soon-to-be victim. You can use a little tape to keep it in place but you may not need to depending on your tube thing (mine didn't need one). Now put your lid back on the toilet tank and your all set.
Step 3: Hide and watch
Now you can just go hide near the bathroom and watch as your victim enters the bathroom. They will do their business and then they will reach to flush (hopefully because please it's america at least try to be mature) and when they do flush the water streams out all over them from the tube, mwahaha.