Deck Construction
Do not build overly large decks, as this will decrease your chance of drawing critical cards late in the match. Build a deck with 40 to 45 cards in it and try to balance the deck with a mix of spell, monster and trap cards. Your deck should have about the same number of monster and spell cards, with one trap card for every four other cards in the deck.
Trap Cards
Place trap cards face down on the field to either trap your opponent or to counteract a move by him. Normal trap cards are only active for one turn, while continuous trap cards such as Solemn Wishes will work continuously throughout the match. Counter traps such as Magic Drain and Negate Attack will remove the effect an opponent's card has on you. Trap cards only begin working on the next turn after they are played.
Overplaying Combos
Try not to overextend your deck by playing a combo that requires several cards. If your opponent is able to counter your attack with one card you may be left with few options the rest of the match. You should build elaborate combos only when playing one will ensure a victory, or if you are so far behind you need a miracle to catch up and win the match.
End Game
Use your most powerful cards at the end of the match. If you play these early in the game you will often find yourself outgunned when you most need these critical cards. Generally, you want to start out with some of your least powerful cards and build momentum throughout the match.