The first thing you will want to do is find a clear surface. I cannot stress the importance of the surface enough. Something slick like tile or the surface of a table will usually make building your card house much more challenging. The best surface is something with a little bit of friction to hold the cards in place a little if you will. Short carpet seems to work really well, or the grass outside can be just as effective. The important thing is to ensure that the environment is free of distraction for your house of cards. Make sure there are no fans (inside) or your house won't get blown over by the wind (outside). Also, make sure you build in a location where people will not be moving around a lot. Footsteps, loud noise, and a wide variety of other things can shake the floor or the ground just enough to topple your house!
Now you are ready to begin building your house of cards. Make sure you have a new deck of cards, as cards that are bent and folded will be harder to build with. The easiest way to build a foundation for your house is to lean two cards against each other. It is crucial that all the cards be as close to the same length apart as possible (so that they will provide two equal forces in opposing directions). Try to set your house cards about three inches apart and let them fall towards each other slowly until they just barely touchÃ¢ÂÂthe two cards should make an upside down "V" shape. Repeat this process moving in a horizontal direction, keep in mind that all the cards should be about the same distance apart.
After you have three or four sets of cards leaning against each other you are ready to move on to the next level. Very carefully pick up a card and lay it face down as a bridge across a pair of the cards leaning against each other. It's generally best to start from the middle and work your way outside, as the middle is most stable. You now have a stable roof completing the first level in your house of cards. Continue to build card teepees on top of previous levels, of course maintaining the same distances between the cards.
If you feel the need to get more adventurous, you can place a solid object such as a book on either of the ends of your house. This will provide stability and allow you to expand farther in the vertical direction. As you get past the first level of your house, you can build as if you would with blocks, that is, make an "H" shape with the cards, two vertical cards and a horizontal card on the top. Be advised, however this setup is less stable than the V shape.