Thanks, Jan. It's said, "A picture is worth 1,000 words." Very true in this case!

In 1956 I was told to put the spool on the spindle so that the thread comes off the back. At that time there were no horizontal spool holders and no large cross-wound spools for domestic sewing machines.

If the spool is cone shaped, it is meant to unroll from the top of the cone. It is cross-wound (or spiral-wound). If your machine has a second spool that lays horizontally, then it is the one you want to use for cone-shaped thread. You can purchase a thread stand for your cone shaped thread if it will not fit on your machine. Joann carries them for about $20.
A typical all-purpose spool of thread unwinds from the side (parallel-wound). Use your vertical spool pin and make sure that it unwinds from the back.
Serger thread is typically cone shaped and is two ply, while all-purpose thread is three-ply. Two-ply thread is lighter weight and therefore doesn't bulk up as much in a serger stitch.
It is also important to use the felt pad that goes under your thread and also the cap that goes on top of the thread spool. If you're having trouble with your thread tangling, it can be related to any of theses things.

This is unrelated to the subject, but if you have misplaced your nets for your cone shaped thread, you can cut tubes out of your nylons and use those. This can be important when you are using a very unruly thread like monofilament.

Jan, thanks for that excellent tip!

Since my featherweight (and my other vintage machines) only have the single vertical spool pin I've discovered a couple of ways to stabilize the larger spools of thread.
The cones fit nicely on the smaller regular thread spools like you get in some sewing kits at the $ store. Or you can use one of the cardboard tubes from an empty large spool.
For the large spools with the cardboard tube center a small strip of craft foam rolled up leaving just enough room for the spool pin stabilizes it nicely and also allows it to feed freely.

I meant to add that thread stands are also ideal for yarn if you knit or crochet.

Interesting thread. Until today, I didn't know it made a difference.

Jan- That's what I've always done... and then I'd mark the top (or outside) of the spool with a "T" with a Sharpie for next time.

Thanks for a great and quick tip. I have been doing a lot of hand applique this month but I am almost ready to start FMQ and I will use this tip to keep from having problems with my thread.

Gosh, never knew there was a way for the thread to come off of the spool. You learn new things everyday.

I was told, however, that you were never to sew with a bobbin thread as the top thread, because it was wound the wrong way (or the opposite way as it was wound on the spool). I know that now, but it has never stopped me and I have to say that I haven't noticed a difference. I only do this when you really need the color that is in the bobbin and you don't have anymore on the spool.