My relationship with sewing is a very chicken and the egg situation. Do I struggle with sewing because it's hard or is it hard because I don't practice enough? It's difficult to say, but I can tell you that making these four pennant banners was quite a struggle. Most of the blame belongs with my machine, which was being particularly temperamental, but there is always user error to consider. I'm here to tell you, though, that persistence pays off.
I used this tutorial, which was really great. I made a couple tweaks, which you'll see. I bought fabric at Joann's, most of it from remnants. If you get about a half-yard of five types of fabric, you'll end up with enough triangle pennants to make four banners.
I grabbed a piece of cardstock and, using a ruler, measured 7 inches across the top and approximately 9 inches to the bottom point. I cut the template out and then used it to lightly trace the shape with pencil on my fabric. I didn't have a rotary cutter, so I used scissors, but you can use a rotary cutter. I won't lie...this is pretty tedious work. But in the grand scheme of things, you can do it while watching 2 1/2 episodes of "Scandal."
Ultimately I had a stack of about 48 triangles (a few got tangled in the machine and had to be sacrificed). I then sewed the sides (not the tops) of each pennant, then pinned them side-by-side to double-fold bias tape, leaving 12 inches of slack on each side. Double-fold bias tape has a long side and a short side; be sure to put the short side in front.
Once pinned, I sewed the tape from end to end and — voila! — I had pennants.