Lost Cities-- Expedition started by the opponent

[Stephane D.]

   How do I score my ponts when an expedition as been started by my opponent?
And do I have to respect the ascending values of the cards anyway?

[Rod S.]

Both players can do the same expedition.  Your cards have to be ascending.  The opponent's cards have to be ascending.  What your opponent plays has no effect on what you may play, except that you'll obviously never get a card that your opponent has already played.  The opponent might play 3,4,5 and then you jump in with 2,7,8 and then your opponent plays 6.  Or whatever.  Your score is determined by what you played.

[Lena H.]

Yes, you have to respect the ascending cards. But of course you are allowed to skip a card if your opponent has already placed it.
It is also better not to place a card in the middle, that he might still need. If he just placed a 6, you shouldn't place a 7 or higher in the middle.