I won't reiterate the rules about using two hands, but I felt I should add a couple more important notes when giving/accepting business cards.
Even though many Korean businesses litter the sidewalk with business cards (either by high speed scooter or someone walking and randomly dropping piles of business cards at your door), if someone hands you their business card and you would like to do business with them someday you need to be super respectful.
1) Use two hands
2) Treat it like they have given you something amazing. Spend some time looking at it and maybe even comment on how nice the design is.
3) Make sure they see you put it in your wallet.
4) When you put it in your wallet, don't stuff it in the back with all the other cards. Put it in the front in the high use zone (where you stick things like credit cards).
These rules may sound silly, but they can go a long way to building a successful business relationship with someone.
Now... up until now it all makes sense right? It is a little over the top but you can see where they are coming from. This is the crazy thing. In Korea (I am unsure about other Asian countries) businesses will often pay scooter drivers to drive around the streets with huge wads of business cards to ninja throw at doors.
The picture above is the front door to my apartment building. I have never seen anyone pick these up to do anything other than throw them in the bin. Why on earth would someone pick something up that has been on the filthy ground? It is a huge waste and frankly I view it as littering. Not only that, but given what I said about treating business cards like they are something special, this seems highly illogical doesn't it. Welcome to Korea.