It's all very simple. First, you must go on a nice walk and capture leaves from the ground (I will admit that I did reach over the fence on more than one occasion to steal some lovely leaves. My reasoning was that they were just going to fall anyway, right?! So finders keepers.)
Then, you must give them a good coat of Mod Podge, front and back. After they dry, let them really flatten out under a stack of heavy books. I let them do this overnight.
Using your machine that sews, connect them by placing one leaf after the other, no backstitching required. I must tell you, sewing leaves is rather crunchy! And I hope I didn't accidentally fill my machine with leaf crumbs. Oh well.
And I regret to tell you that I have no estimation on the life of this garland. My reasoning was that the Mod Podge would sort of 'seal' the leaves, thus slowing down the deterioration process. But smarty-pants Evan thought it might be better to first press the leaves, letting the moisture escape, and then apply Mod Podge. But who has the patience for that kind of thing? Not me.
Besides, I think it might be kind of fun to have the garland slowly turn brown. Because by the time it's brittle and old, it will be time for winter. And Christmas garlands! Or maybe that's just me being impatient.