Some useful phrases - Germany

When the sweet old lady (who's probably 99, and most likely knows no English) next to you in the Bahn leaves half her parcels behind, how do you call her back? 'Excuse me, Ma'am' doesn't work. 'Yo Oma' is probably not the best approach. So?
In fact, how do you address women not known to you in German? And while we are at it, men?
Also, in the gym, what is the easiest way of saying 'Dude, can we do this alternately?' in German, without involving a lot of you-me-you-me gestures?

Thanks for the help, in advance!

good questions.... what on earth do u say?
P:S love the 'yo Oma' part !

Simply shout (you will have to speak louder if she is an old lady): Entschuldigung, Sie haben was vergessen! This normally gets everybody's attention, she is bound to turn her head around, not only her though. That way you completely ignore addressing her directly with Sie alte Dame or something equally unflattering.

Same principle, avoid a direct expression. Simply say: "Wechseln wir uns ab?" With a smile of course.

I greet the kats at the pub with "Was los bitches (no capital b though)".

Entschuldigung, gnädige Frau, aber Sie scheinen Ihre Pakete vergessen zu haben.

Though I think on the Ubahn "Yo Oma" would work just as well

No need to even waste a yo there.

"Junge Frau!" will get her attention as well

Well, I think I will go with the gnädige Frau thing. Very Prisoner of Zenda, if you know what I mean
Thing is, if I ever mix the two situations up, and say to that small mack truck in the gym who's doing squats with every weight plate in lower Saxony: 'Entschuldigung, gnädige Frau, aber kann ich diesem (weight plates??) nehmen?', then probably they will be scraping me off the carpet in an hour.
Ok, bad joke. We all can't be brilliant. And I happen to be rather faux-pas prone.

"Gnädige Frau" is dated. You won´t hear it from a native speaker anymore.

"Entschuldigen Sie, sie haben Ihr Paket/Ihre Pakete vergessen"

Remember there´s no difference between Ma´am, Mrs and Miss in German. Just use the polite "Sie".

'schöne Frau' always works

That depends on the age and the background of the speaker.

My neighbour Generalmajor FrieherrAugust Friedrich von der Neunhausen* would always use it.

*Not really but I have heard it from some of the older generation.

Gnädige Frau?? At the opera or a ball in Vienna perhaps...

A hearty "Hallo, Sie da" should also work (for the linguistically challenged). You'll have to alternately point to her and at her forgotten parcels, but she (or someone around her) should get the message.

The last time I can actually remember it being used was at a Christmas ball a few years ago when I introduced my wife to some crusty old Oberst from one of the more "refined" German armoured regiments. (I think he was part of MNC NE) but he was pretty damn old!

And now I think of it this was actually last century (1999) so pretty old fashioned then

Your Oberst was probably one of the "Ich schwöre bei Gott diesen heiligen Eid, dass ich dem Führer des Deutschen Reiches und Volkes, Adolf Hitler, dem Oberbefehlshaber der Wehrmacht..." brigade, then.