Wow, there are some over-complex answers here! All correct, but over-complex nonetheless!
GR, it's actually quite simple. If you're tracking to/from a VOR, you set your OBS to be roughly equal to your heading. The equipment works everything else out for you, and displays the correct indication. That's it.
(What then happens is it compares your OBS setting to the radial you're on. If they're more than 180 degrees out, it displays a To flag, otherwise it displays a From flag.)
The only confusing part of using a VOR is if the OBS is not roughly the same as your heading. Because the VOR display has no idea what heading you're on, if you're on the 090 radial, with 090 set on the OBS, but tracking 270 (i.e. to the VOR), it will display a From flag, because it doesn't know that you're actually flying away from the beacon. The needle will also indicate in the wrong sense. But this can be avoided by following the simple rule: OBS is roughly equal to your heading.
(Of course, that only applies to tracking to/from a VOR. If you just want a position fix, you always find a From flag, regardless of your heading... but that's a different story, a different use for the same tools.)
Hope that helps!
FFF
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