Apart from Jellby's first reply I don't think these answers are very helpful.
Despite more or less a common convention system across the platform, people play differently, so my first and the most important suggestion if you play with people you don't play frequently with is to ask before the game start how they would like to play in such situations. Always marked first unless you have a proof it's not the card you should be playing is a good default answer. This is how most masters will play anyway. Low focus/skill masters (still a majority of players with 700+ ELO) will even sometimes play marked first if they have a negative number on that card when the information is no longer visible on their cards (for example they were marked single 2 to play a card and already played it).
When you play with people you know well, you can make sure they would read context better.
Let's take Blacktango's first example (simple prompt) and add a bit of context:
1) simple prompt
Alice clues Bob on two greens
Bob plays 1g
Charlie discards
Alice clues Charlie on 3g
Bob has no reason to assume his marked green is not 2g, so plays it
2) finesse despite having marked card
Alice clues Bob on two greens
Bob plays 1g
Charlie discards
Alice sees 3g in Charlie's hand that she can easily clue with color or number, but discards
Bob also observes 3g in Charlie's hand and notes that his green is unlikely to be 2, because Alice would clue it to prompt him, then discards
Charlie discards
Alice clues Charlie's 3g
Bob thinks again why Alice did not clue it a round before (were there more important things to clue? were there plenty of tokens, yet all players discarded?) and allowed some useful (noncritical) cards to be discarded and figures out his marked is not 2g, but he must have drawn it the previous round, so plays leftmost
The above examples are when you only need to play a single card and decide between leftmost or marked, but the same logic applies when you have to play both leftmost and marked.
3) prompt + finesse
Alice clues Bob on two greens
Bob plays 1g
Charlie discards
Alice clues green on 4g
Bob knows he has two cards to play and no reason to believe his marked is not 2g, so plays it first
Charlie discards
Alice discards
Bob plays 2nd leftmost card, finding 3g
4) finesse + prompt
Alice clues Bob on two greens
Bob plays 1g
Charlie discards
Alice and Bob observe 3g on Charlie's hand, but Alice is uninterested in this card and game continues for a few rounds and Charlie finally discards it (or it's even possible he doesn't yet discard it, but all players discard at least once and Charlie draws 4g at some point)
Later Charlie draws 4g and at some point Alice clues it (as 4 if Charlie still has 3g in hand)
Bob remembers Alice was not interested in 3g in Charlie's hand earlier, so he noted it's very unlikely to be 2g, so plays leftmost first
I'll reiterate I don't recommend trying these kind of clues (example 2 and 4) that require some good context reads with people you don't know well enough. Simpler is often better and using 1 more clue to show exactly where 2 and 3 is won't break the game and make it impossible to score max most of the time.
