Should I learn Actionscript 1 or 2?

If your goal is just to learn basic scripting principles, you might get something out of it, but otherwise you're better off finding more recent tutorials on the Intertubes. There are plenty of them, most of them free.

Actionscript 3 shipped over a year ago. Might want to move on from 1 and 2.

Agree with both comments from above. Actionscript is all based upon the same basic principles but each (eg. 1,2,3) have their own uniqueness. It would honestly depend on what version of Flash you are using as well - if you're using CS3, definitely look for tutorials online, like segdeha said there's countless tutorials - good luck! Learn easing scripting, it makes animations look way more professional!

As with most upgrades, I tend to prefer the newest one better. I love actionscript 3. There's plenty of tuts lying around for all three though. I'd say if you really want to get into the principles and the history of the language, start with one. If your just want to learn to use it and do fun stuff, go straight to actionscript 3. Good luck!

AS1 would be futile as not even Flash Lite makes use of it any more. AS2 is very similar but still being used. If you’ve got a good understanding of object oriented programming, I’d suggest going directly to AS3. However, if you’ve little programming experience, start with AS2 as it is far more forgiving and easier to break into though it does have issues (mainly scope issues which AS3 resolves). I would suggest aiming for proficiency in AS3 if you plan to do any serious Flash development professionally.

As for where to learn, there are a bevy of resources on the web. You shouldn’t have much trouble finding forums and tutorials to meet your needs. The Adobe documentation on AS2/3 is pretty decent and worth referring to when it comes to technical information.