You need to get Between 20 and 26 on your piles as fast as possible before your opponent does.
To place cards you first need 1 card on each 3 pile area, the 2nd card on a pile decides whether the pile is ascending or descending (so if you first put down an 8 and then put down a 6 the pile is going down from 6). You can then place any card ascending/descending in the same manor from the last card on the pile.
The other way you can put a card on a pile is by suit (Hearts, Clubs, Spades, Diamonds) from the last card on the pile. If you place a card by suit it doesnt have to be in ascending/descending order, and the same goes the other way around.
So if the pile was 8club 6 diamond, I could then place a 7 diamond on the pile, which would also change the pile from descending to ascending, not that it matters because 8 + 6 + 7 = 21, which is enough to make it a winning pile. Now you just need to do it for the other 2 piles.
Placing a Jack next to one of yours or your opponents cards strips that card from the pile.
Placing a Queen swaps the suit and ascending/descending order of the pile
Placing a King next to a card doubles that cards value
If you read this far then congratulations, youve now learnt the insanity that is Caravan, dont forget your giftbag on the way out.