#21 Of two options, choose the safer one
Sometimes, a teammate gives you a clue that looks very much like a play clue, while you already have something else safer to do (a play or a discard). In most cases, it’s best that you first take the latter, safer option and only then the former one, if your teammates don’t warn you that it is unplayable.
1) You have a 2. The only unplayable 2 is green. You receive a clue on a single green card. Your 2 is therefore playable, play it first.
2) All 1s are in play, some 2s are in play. You have a 2 and receive a clue to a single 3. Play the 2 first and only later the 3.
#22 Levels of risk
See this article.
#23 Discard a duplicate
This technique is about discarding a known, playable card to tell another player they have that card.
Alex has a 2, but doesn’t know it’s blue.
For some reason, you know one of your cards is b2. If you play it, Alex might end up playing his 2 at some stage (and bomb). Or it will cost a clue to stop him from doing it.
So the best option is for you to discard your b2. Alex will see think “WTF?” and end up understanding his 2 is blue.
#24 Anticipated clue
You receive a play clue. Your LH1 has the card that comes right after yours. Following the “give play clues ASAP” principle (basics level 2), clue that card now. Your LH₁ should understand you know you have the playable card and his is therefore the next playable one.
#25 Prevent consecutive discards
If two players have the same card on the chop, somebody should save one of them to avoid them both being discarded.
This is why when you receive a chop clue that looks like a “play”, in addition to all due precautions, also check out other people’s chops.