The cards you throw away are just as important as the ones you keep. Unless you are either a complete idiot or a beginner, each card in your deck has a purpose. Therefore, there are no "throw away" cards in higher levels of play. Of course, there are cards like Sinister Serpent and Night Assassin that are meant to be discarded, but that is their purpose so it doesn't contradict what I said earlier. To me, discarding is just a term used to describe the movement of card(s) from a higher "pile" to either the graveyard or Removed from Game. From highest to lowest pile, the order is Deck, Hand, Field, Graveyard, RFG. Even though cards that go to the RFG pile aren't called discarded, I still use the term.

        Basically, you can say that I take a page out of Yugi's book and have respect for my cards. The trouble with discarding is that you might have use for that card later. There is no way to tell this, but there are ways to make an educated decision on what card(s) to discard. You must consider ALL aspects of gameplay in order to do this. I might be digging too deep for you people without shovels to follow, but try to understand. At no point in the game should you be focused on one part of the game. Not only both sides of the field, but consider the other active piles. The deck, for example is probably the most overlooked factor in the duel. The hand, or lack of it usually draws the most attention from both players. The field is the middle ground, where your focus is only drawn when there's "action." I stress keeping track of the graveyard a lot too, but people don't do it enough. Life points are obviously important too, but how much you have depends directly on the happenings of the others.

        Why mention the aspects of gameplay at all? Don't we know them? Knowing and using efficiently are two different things. This will make sense later. You discard smartly when you either have something to replace the card, the card can be revived, another copy of the card is active, or the card is truly expendable. You won't discard a 4 or less star monster unless you have another to back you up would you? The thing that I'm stressing here that ties into knowing what to discard is probability. In order to utilize this completely, you must have knowledge of your total deck size, your card ratios, and your cards that are currently in play, have been played, or have already been played. You add up the total amount of cards you have not in your deck, then compare it to the amount you have left. Consider what type of card you need (Spell, Trap, Monster) and know how much you have left relative to the amount you've already expended. What?

Based on what you've used already and what's left in your deck, determine whether or not the card is expendable.

Monster cards especially can't be taken lightly. There used to be fear regarding what monsters you could and couldn't drop into the graveyard. With Monster Reborn gone, what hits your graveyard remains yours with a few exceptions. However, if you throw them away without thinking you'll end up being pummeled no matter how skillfully you can use your other cards. You need to make sure you have some way to get a monster to replace the fallen one... before discarding just keep in mind the probability of drawing another playable monster. All this probability stuff, it doesn't take long to run it through your head when you get used to it really.

        So far, what's been described is discarding from the hand. What about things like Painful Choice? What sets Painful Choice apart from most cards is that it is your opponent's choice. Therefore, it is best to think Murphy's law and expect the card you want them to pick to end up somewhere else. For me, Painful Choice serves the purpose of getting a glimpse of what cards I have left and thinning my deck. It's not a reliable search engine as Computer Search was to Pokemon, not even in the slightest. For PC you have to choose cards that you can part with after considering the need for them later or cards that can be revived. I can't give you advice on what works best- that comes from experience.

        Manually from the field to the graveyard... generally that happens through something we YGO people like to call tributing. Usually, you'll only have 1-2 monsters to choose from on the field. Just like regular discarding, being smart about how you go about tributing is vital too. You need consider how likely it is that your monster will survive on the field, and if it will hit it at all. If it's probably not, then just keep your monsters on the field and knock away. Not only does this serve the purpose of confirming whether or not the face down card is dangerous, it also saves your tribute monster so you can play it later or discard it for something more practical. Maintaining card advantage is something to keep in mind in the hustle and bustle of a duel.

        The other place cards can be "discarded" manually is the graveyard to RFG. Whether it's a monster (most commonly) or a Spell or Trap the decision, even if not as important still is important as above. The thing that sets apart RFG from the above is that it is pretty much permanent, thus has the highest chance of coming back to bite you in the ass via Fiber Jar. Unless you run Dimension Fusion or RftDD, you should always remove weak monsters. Baring if it will win you the game, there is a chance that you'll draw a recursion card later or a Fiber will go off and you'll be stuck with nothing good to get back.

        How you get rid of cards can and will affect the tide of the duel. I'm 100% sure that each and every one of you has come across a time when you made a bad discarding decision and if you didn't it could have won you the game. There's no way to completely predict if you will need the card, but by making educated choices you give yourself the satisfaction of knowing you made the best choice at the time and have no regrets. ^_^; Trust me, it works. Any par duelist has the ability to sweep any player straight out of a competition.