No matter your favourite colour, all deckbuilding rules are the same. To create the best deck possible, you cannot cram 200 cards into your library (unless you are playing Battle of the Wits) or ignore lands.

Step 1: The Idea
Some people start with a theme, like soldiers, or a single card - usually a godlike rare like Psychatog - and build a deck around that focal point. You will want to concentrate on an organized theme. Putting a bunch of good cards together can work, but a deck with a purpose works better.

Step 2: 60 Cards, Not 100.
A 60-card minimum is the standard in most tournament-legal decks. There is one simple rule: Never go over 60 cards. The more cards you add, the more cluttered your deck becomes. You want the best odds for drawing the cards you need. The more cards you have, the worse chance of drawing that power card. Important second rule: Include at least 20 lands in your deck. Even though you may want to load it up with creatures and spells, your deck needs mana to cast everything. There are times when you need a little more land or a little less, but the best method for beginners is to have at least one-third of your deck lands.

Step 3: The Mana Curve
Even though the biggest bombs are game-winners, it is likely you will never cast any of these expensive cards if your deck holds nothing but six-plus mana spells. Pay attention to your mana curve. You want to have pressure early game, rather than sit back and take a beating while you accumulate your lands. A basic model would be:
    14     one-mana spells
    14     two-mana spells
    08     three-mana spells
    04     four-mana-or-higher spells

Step 4: Answers and Antidotes
Do you have a way to win - whether by cheap, fast creatures, flying angels, or direct-damage? Make sure your deck can win. You also have to have an answer to the decks you will commonly face. Do you have a way to stop mass armies or one fat creature? Your deck needs to outrace your opponent to the life-total finish line.

Step 5: Practice Makes Near-Perfect
We all know the only way to get better is practice. You will find your first deck never works exactly the way you want, but take mental notes of what is not working while you are playing. Make the appropriate changes and try again. Eventually, your new deck will be on its way.