Final Fantasy IV

There is no "should" or "shouldn't." How you play the game is totally up to you.

That being said, if you want to get the most out of your game there are two augment guides (stickied topics) on the message boards and Action also has another really good augment guide in his walkthrough.

It is recommended that you follow one of the three guides.

The short answer is "yes", if you want to get more than just one augment from each, you will need to give both of them one or two augments before they leave. The same goes for FuSoYa, and any other character that isn't a permanent member of your party (the exception being the twins, who only need 3 augments between them, and at least one of each).

You should put augments on those characters, especially Yang since he gives the very useful Focus augment. Just give them the augments like Tidal Wave or Cyclone since they don't help much anyway.

Yang should definitely get at least one augment so you can get Kick. This is very useful when combined with Draw Attacks and Counter. I disagree with MrCactuar on which augments to use up, though, as Tsunami and Whirlwind both give very good stat boosts for the higher levels (on any level above 70, stat gains are determined strictly by which augments are equipped).

Give them augments like curse, bardsong, and auto-potion. all the useless ones that no one really needs

i would say wait for the second play through so that you have plenty of augments.

that said, you can get more augments when you do this as early as possible. give at least every temp. member 2-3 augments and go through with the game and you will get the most of it. You have 3 chances though, so you don't have to be hasty