This article is from the Model Rockets FAQ, by Wolfram von Kiparski with numerous contributions by others.
From Kevin Kuczek:
First I reinforce the end I plan to tie the streamer onto with 1/2"
mylar tape (from ASP) folded over so you have 1/4" on each side. Next,
I tie a small 1" loop in the kevlar, pass a piece of clear packaging
tape through the loop then apply it to a corner on the streamer- one
half of the packaging tape gets applied to one side,the other half to
the opposite side. Need to made sure you get the packaging tape that
stretches and is can't be torn vs. the mylar/polyester type that does
not stretch and is easy to tear.