This game is unlike the standard memory game in that you're not restricted to a certain number of attempts; because it's PvP, all that matters is that you finish the board before your opponent does.
An ideal strategy would involve both speed and memorization, but because these are alien faces rather than numbers, letters, or flags – items that can be quickly and accurately recalled with one or two words – memorizing the entire board, or enough of it to be helpful, is probably out of the question.
That's OK, though. You don't have to memorize the whole board. In theory, you'd only have to memorize half of it at most, because everything beyond that would be a match, but in practice, all you need to remember is one or two faces.
This is the strategy I would recommend:
- Flip cards until you get a face with a feature you can easily remember: horns, visor (like Geordi La Forge's visor in ST:TNG), three eyes, X eyes, whatever. Call this Card A.
- Flip cards until you find its match. DON'T flip Card A again until you find the match: this way you go through cards twice as quickly. This is Card B.
- Once you find Card B, then flip Card A and Card B to get your match.
- Go back to Step 1 and repeat until you're down to 2 pairs; after that point, use brute force to uncover matches. (Don't bother purposely memorizing at that point: there are only three possible combinations. With cards 1 through 4 left, you can touch 1 and 2, 1 and 3, 1 and 4 to figure out where the remaining pairs are, and do it faster than you can read this sentence.)
By starting with the easiest faces to remember, you'll shrink the pool of remaining cards, hopefully to the point where the final pairs are easily distinguished, and in the process, you may flip a couple of pairs completely by accident.
With practice, you may remember more faces, so you can improve your time by modifying Steps 1 and 2 to look for multiple pairs instead of just one. (At first, you'll find Horns and want to match it. With practice, you could get to the point where you flip Hat-Horns-Three-Visor and can remember all four of those; this will improve your speed even more.)
I've used this method successfully in the matches I've played (not very many, mind you). I do have an excellent memory myself; it's more suited to letters and numbers rather than faces, so it's possible that if you have a memory for faces, it may be better to try to memorize them first, but I suspect speed is most important in this game, and thus you want to focus on quick matches rather than memorization of multiple cards.