When you receive a clue that targets more than one card, some techniques enable you to determine which of them you should play.

Here we will see in which cases it makes more sense to play the oldest card first. Let's call this rightism (as opposed to well-known leftism), assuming your chop card is to the right (you discard from the right).

Basically, these are some cases where all cards of the clued kind are either worthless or playable.

Starting 1's

The game has just started. R1 and Y1 are already in play or are about to be played.

You have not discarded or played any cards yet. You receive a 1 clue and your hand looks like this:

1)

? 1 ? 1

The best option is to play your rightmost 1 first. If it was no good, your teammates would have let you discard it before clueing 1, so they wouldn't need another clue to stop you from playing it. So the rightmost 1 is the safest one to play in this case.

Clueing 1 may have been the only way for them to save it and get it played, even if the leftmost 1 is rubbish.

2) ?11? or 1?1? or 11??

The same reasoning is valid, since you need to find a way to determine the most likely playable card. And the only logical reasoning you can rely on is the one previously explained.

3) The same goes when no 1's are in play or about to be played, since your teammates need you to be predictable, just in case.

4) The same may sometimes be valid even after you have played or discarded one or more cards. Carefully examine situation in these cases.

Last playable card(s) of a kind

1) Number

All X's are either already in play or playable (where X stands for any number). You receive a X clue and your hand looks like this:

? ? X X

Unless game end is very close*, same reasoning as above: the rightmost X has to be valid (if not playable, depending on tableau status), otherwise your teammates would have let it die before clueing X.

2) Colour

Only one card of a given colour (X) remains to be played. You receive a X clue.

Played cards status:

B2 G2 R4 W4 y3

After the clue your hand looks like:

a) ? W ? W

Unless game end is very close*, same reasoning: if rightmost W was rubbish, they would have let it get trashed. But then, why not clue 5? Because with a 5 clue, you would have held it, not played.

b) W ? ? W

Slightly different reasoning: if W4 has been in play for a while, a 5 clue would have been clearer for W5 if leftmost. So it has to be rightmost. Why not 5 if it is rightmost? Again, because 5 would make you hold the card, not play it.

*imminent game end is a case of high exception, where you sometimes need to give clues in the wrong timing because there will otherwise not be enough time to do everything that is needed.

You recently discarded an easily cluable playable card

Example: all 2s are either playable or rubbish. You have just been allowed to discard Y2, which is playable, while it would have been easy to clue it as 2. Next thing you know, you are clued 2 on your newest card and another card. Play the latter; it has to be Y2 or they would't have let you discard Y2 earlier.

This is a simple case, there must be more complex cases where you could reach the same conclusion.