According to the rulebook some Action cards need to be prepared with a Manoeuvre action in order to be used. The example(page 60-61 in the rulebook) states that the Accurate Shot action card should be prepared before it can be used.In the example the character spends his free manoeuvre to draw his long bow and then,as the example states,he needs another maneuvre to prepare the action card.Why an additional manoeuvre is needed?Nothing is stated on the Accurate Shot card...How can we distinguish which action cards need manoeuvre to be prepared and which not?

Thanks in advance.

The example is incorrect (and noted in the FAQ). Accurate Shot does not require a prepare manoeuvre. If an action has any requirements they will be listed on the card.

As a house rule, I've allowed players to "take extra time preparing" an action or skill test.

Depending on how interestingly or creatively they describe the preparations (other than just "uh, I take an extra maneuver") I'll toss 'em a few extra fortune dice.

The card will specifically state in the requirements that it needs preparation, or that using the prepare manouver gives it a bonus of some kind.

If it doesn't say it's necessary, then it's not. The example is in error.