Hot Glue Gun & Glue Sticks
Felt - various colours
I went with yellow & white pennants as those were the only colours I had enough of in full sheets of felt. (I would have liked to used multiple colours for the penants but wanted to use up what I already had)
I cut out a triangle from one felt sheet and then used it as a template for all of the other triangles. I got three triangles from each sheet of felt.
I drew out the letters on various coloured felt pieces, cut them out, and hot glued them with the ink side down.
To add some more colour to the banner, I used some more triangles and added colourful circles to them. I used these before "Happy" and between "Happy Birthday" and at the end.
The easiest sewing-free way to hang them I thought would be to make little tabs and thread the cord through. Like a tab-top curtain panel would have.