What happens if the shower arm tightens on the wrong angle? Like 90 degrees from where it should be. Do Iadd a lot of tape or try going further around? Is there a trick to this that only a plumber would know?
Thanks, Gary

The only trick is knowing when to stop.

Remove the shower arm and wrap with teflon tape again. I prefer to use pipe thread joint compound for this.
Once you have the shower arm started, and with the shower arm pointed down, you have to decide whether you can make another complete turn. If you try and can't make another complete turn, you take it out, tape or dope the threads again and start over.

Shower arm doesn't have to be extremely tight. There is not that much pressure on it.