First, before you start to build the deck, we have to decide what will be the archetype to be used, because then we can decide the functionality of the deck and how it had gone. This also will define the ease of summoning, ease of fusion, synchro or xyz. Deciding this first step, we have the monsters of our deck and, most likely, part of spells and traps.
Now to the second point: this is the time to decide the traps and spells of the deck. Some are traditional: heavy storm and monster reborn (which they shall be banished now in September). Others should follow the chosen archetype. For example, use decks hieratic hieratic seal of convocation; Six Sam decks use shien's dojo, shien's smoke signal and help others. Traps in
general are counter summoning (solemns, ced, bth and etc.) and they completed the probable 40 cards from our deck.
Third step: Now it's time to decide what extra deck. The limit is 15 cards, but the decision to use the limit is your decision. Using as a basis the archetype of the deck, which will be decided our
extra deck. If the archetype has special
summoning effects and there are tuners, we can add synchro monsters; using fusion, add some monsters, and, almost always, there will be room for the xyz. With this, we are approaching
the end. Added the extra deck monsters, finalized with the side. The side deck should contain those cards that you can use during a match to change its strategy dueling.We build the side as well as the entire deck, using as a basis the archetype used, but always after the entire deck to be ready.
Perhaps many people will say that I could be more specific, but soon post
an example of deck building to complement that matter.