Some ideas.

Without cheat:
Evaluate the current state of the game and give it a score. Eg: score:=own_life_pts - enemy_life_pts + own_cards_on table;
Of course you will need a much more complicated scoring system.

Then go through all possible actions, give them a score and finally choose the one that has the highest score.

With cheating:
You can use the above, but you should also calculate a score on all enemy moves. You can build a chess A-B algorithm this way (many references to it). A-B is very effective, I wrote an AI once for Maya, where you have to move 6 piles of stones - each of 6 stones. The computer was unbeatable (without cheating, no hidden cards).