I am in the middle of making a garland right now (more about that soon) and am working on making the hanging loop part. After a few different tries, this one is definitely my favorite. It is super easy, looks clean, and can hold a good bit of weight.
For the loop shown, I used some worsted weight yarn and an H (5.0 mm) crochet hook.
For a smaller loop (that might hang on a hook for example), start by chaining 8. If you want your loop to go on a door knob or something larger, make a chain and test the size first by slipping it around the object before continuing.
Insert the hook into the farthest chain from your hook,
and join to close with a slip stitch. Next work a single crochet into the center of the ring for added stability,
and continue with your chain.
To make a loop on the other side of your garland as you are finishing up, make it the same exact way, just be sure to reserve 8 extra chains (or however many you made with the first loop) to create the loop at the end.
To finish, you can weave in the ends as you go, or weave them at the end with a tapestry needle.