There are several things to do in order to make a good deck. The first is to define what you want to do with your deck. Do you want to win games? Do you want to use cool cards or cool combos? Do you want to lose games? Do you want to use a specific set only? Once you have figured out what the objective of your deck is, you can choose your colours. Unless you are making a domain (5 colours) deck, don't choose more than 3 colours. Try to use colours with which you have cards that work well together. For example, Quiet Speculation works well with Roar of the Wurm, but White Knight won't work well with Soul Link.

Once your colours are chosen, select your cards. Cards have several categories, like bounce (Repulse), pingers (Razorfin Hunter, Lava Dart), burn (Shock, Blaze), counter (Counterspell, Mystic Snake), mana producers(Llanowar Elves), fatties (big creatures;Silvos), discard (Duress), and many others. The main point here is to choose one or two categories to focus on. At least one of these categories must kill someone. There's no point in using just counterspells, unless you use some flying creatures or burn spells or something to kill them. If you're making a deck that you want to win with, make sure you have a quick, efficient way to kill someone. Make sure you know the strength and weaknesses of your colours. Blue is good at clearing the board of creatures but is weak against burn spells and enchantments. Green can destroy enchantments and has big creatures but can't often prevent their creatures from being destroyed by black spells. Red has good damage spells and agressive creatures, but falls quickly to enchantments. White can protect their creatures and enchantments only second to blue, but can find it difficult to deal with blue bounce spells.

Anyhow, the point here is to choose categories that your colours are good at. Also, choose categories that will help you kill someone and focus on them and supporting them. Figure out how you're going to win most games. Is it by using Wonder, or Overrun, with a horde of small creatures? Or will you rely on a few powerful creatures like Guiltfeeder? Do you use special cards like Coalition Victory, or Battle of Wits? Focus on supporting these winning cards. For example, use cards like Roar of the Wurm, Ray of Revalation and Aquamoeba to support wonder, as wonder, ray of revalation, and ROTW can be discarded by Aquamoeba to great effect. Example two; use land search cards like Harrow and multicoloured creatures like Darigaaz to support a coalition victory.

Another focus of decks should be to prevent opposing decks from winning. How many of such cards you put in depends on your deck. For the above example with wonder, ray of revalation is a good card to prevent other decks from winning, as it destroys their enchantments. Be careful not to focus too much on preventing others from winning, as the main focus of a deck should be to win, not to delay others. Throwing in cards to counter the strategies of others and boost your own is ok however, like Aven Cloudchaser in a bird deck, or Order of Yawgmoth in a Magrim deck. In fact, decks like magrim will benefit much from those cards. The amount of "stalling" cards depends a lot on your deck. If your deck is agressive, cut them to a minimum. If it works on victory through subversive ways, like magrim, then increasing them can help.

So in conclusion, focus on winning through a specific theme, and you will build better decks. Look to more deckbuilding articles in the future that focus on specifically themed decks
-trouble_fish