There are probably lots of other people who have written deck building instructions for beginners. But I'm going to write another one anyway.
This "article", if you want to call it that, is meant to give a basic outline of the deck building process and the various facets of a functional magic deck.
Focus:
The first thing that any Magic pamphlet or tutorial will tell you to do is to pick a "Focus".
The focus of a deck relates to two things:
1: The manner in which you want the cards to interact with each other and/or the opponents cards.
2: The win condition.
For those who have never played magic the first point is pretty meaningless. But the second point can help a lot, if you understand the fundamental point of the game. That is, to win.
In regular matches the win conditions a limited to, your opponents life total becoming zero and cards with special win conditions. Such as Azor's Elocutors, (See side board). There are many ways to insure that you have a consistent, reliable win condition in your deck. So, for the most part, you need to simply make sure you include one.
Once you have played a few matches and understand how the cards interact you will be able to build your focus around how you want to play, instead of simply focusing on having the ability to win. But that is outside the scope of this article.
Balance:
The balance of a deck relates to your color coordination.
For one colored decks, deck balance is a non-issue. However, for any deck with two or more colors deck balance is very important.
On this site, the deck balance can be checked by looking at the "Mana Symbol Occurrence" diagram and see how many times any given color is used among the spells in your deck. An unbalanced deck will have a much higher number for one color than another. Once you have been playing for a while you will learn what works and what doesn't work with regards to deck balance.
For a beginner, I recommend that your deck balance be within 10 "mana symbol occurrences" of each other.
Mana Ratio:
The mana ratio relates to two things:
1: The percentage of land in the completed deck.
2: The ratio of land types.
The recommended percentage of land in a magic deck is 40%. This can be checked with the pie chart under "Type Breakdown" in the "Deck Stats" tab of the MTG Vault deck builder. This percentage is the recommended amount for beginners. As you experiment with your deck you may find that it works better at a slightly higher or lower percentage. This is just a matter of practice. I keep my decks somewhere around 35-40%. Depending on the decks build.
The land type ratio relates to how many lands of each color you have in the deck. In general, you should try to keep the number of lands between the different colors the same. For example, if you have a 60 card green/white deck you should have 12 white land and 12 green land.
Mana Slope:
The mana slope or "mana curve", (as it is called on this site), relates to the number of cards with a given mana cost.
The "mana curve" chart in this deck builder provides a graph showing how many cards of each mana cost there are from lowest to highest.
In a deck with a low mana slope more than half the spells have a mana cost between 0 and 2. In a high mana slope deck more than half the spells cost between 4 and infinity. The spells that cost 3 mana to cast can be classified either as high or low. Different people calculate it differently. I exclude the 3 cost spells and count them as a third set. So for me a low mana slope would be:
17 cards between 0 and 2
13 cards that cost 3
15 cards between 4 and infinity.
The import thing here is not how you count the slope. Rather, it is that you keep the slope as low as possible and still maintain your win condition.
The lower your mana slope the faster your deck will be.
Speed:
The speed of a deck is determined by several factors particularly the mana slope, (see above), mana ramp and card draw.
Mana Ramp is any card that increases how much mana you have available to spend on spells and activated abilities. For example: Elvish Mystic, (see main deck). The earlier you can play your mana ramp the more effective it will be.
Card draw is pretty self-explanatory. The only guideline for card draw is to make sure you aren't drawing one card using a card that has no other use. The reason for this is basic statistics. Unless you are drawing more than one card or have an additional ability or use for the spell, it's simply taking up space. For example: Abundant Growth, (see side board). Note: when Abundant Growth is used in a multi colored deck the second ability is useful and validates its use. However, for this example I am assuming the deck is solid green. In which case, the second ability is pointless and the card draw isn't worth while. Also note, the lower the mana cost of your card draw the faster your deck will be.
Flexibility:
The flexibility of a deck relates to how it handles other decks.
You should try to include at least a couple of each of the following card types in your deck. You probably wont be able to get all of them in every deck, but the more you have the better your flexibility will be.
Creature destruction or control:
Any card that eliminates or limits your opponents ability to use their creatures.
Artifact and Enchantment Destruction:
Any card that eliminates your opponents artifacts and/or enchantments.
Blockers:
Any creature you can use to block your opponents creatures. (Creatures with abilities that you'd rather use instead of blocking don't count toward your blockers).
Protection:
Any card that prevents you or your creatures from taking damage. Or diverts an attempt to eliminate or control your permanents.
Flying:
Many decks have an extreme weakness to flying. So, have a contingency for opponents using flying.
Life Gain:
Any card that increases your life total. No duh.
Combos:
Combos relate to chaining your cards together in a manner that produces an effect greater than the sum of their parts.
There are tons of great combos, and for the most part, you simply have to look at other peoples decks or sift through hundreds of cards to figure out what combo options are available to you. There are no guild lines for how to build a combo, except, read the cards and fully understand every word used and look up the comprehensive rules at wizardsofthecoast.com. Combos can be very powerful and a lot of fun. I personally think they are the best feature of any good deck.
Multi-Player:
One v One dueling is ok, but two v two and free-for-all is where it's at. The more people you have, the more dynamics the game can adopt.
The main thing to consider when building a multi-player deck is whether or not the cards you choose to include benefit or harm your team mates.
For example you probably don't want to use Day of Judgement, (see side board) when your team mate has a lot of good creatures on the battlefield. On the flip side, using Debt to the Deathless, (see side board) would help your team mate and hurt all your opponents. All in all just be careful what you use in your multi-player decks, otherwise your friends may not want you on their team...ever.