Introduction
A good deck is always balanced & Consistent. A good ratio is usually around 20 monsters, 10 spell and 10 traps (but all decks vary slightly) because having a heavy count of one type of card will lead to bricked hands that you cant
do anything with. Often neglected is the importance of keeping your deck at 40 cards. Imagine you're playing a card game where one golden card can guarantee you victory. Wouldn't you want to draw that "Golden Card" every time to achieve that instant victory and satisfaction? Unfortunately for you, 39 cards must stand between you and that golden card. Now, taking into account this scenario, why would you want to decrease your chances of drawing that golden card by adding more obstacles? Each card you add beyond the 40 minimum takes you one card away from drawing that boss card you need to emerge triumphant.
Also a deck should always have good draw power / deck thinning abilities and be able to search out key cards when needed.
How many copies of 'X' card do I need?
It's no secret that playing multiple of a single card helps you accessing it faster and earlier in the game. Using many copies of a single card allows for more uses and re-uses
Run 3 of cards what you need to see regularly and rely on.
Run 2 of cards you need but don't need to see as often.
Run 1 of cards which help you improve your gamestate but only need on a rare occasions.
[blur]Synergy[/color]
It is very important for a deck to work together and have synergy with one another . Archetype decks have synergy since the cards were designed to work together.
you don't want too much going on at once in a single deck because it isn't going to work well together.
[blur]Eliminate What Doesn't Work[/color]
I don't care how much you love a certain card or how cool you think it is if it doesn't work in the deck its a dead draw and will potentially lose you the game.
You wouldn't Run BLS in a deck with no Light or Dark monsters would you?
Avoid Situational Cards
Situational cards refer to those cards who only have a limited use. While they may have great effects, they're useless most of the time or only works with a select few cards or in some cases outclassed by superior cards.
Remember, the fewer restrictions to activate powerful effects, the better.
Extra deck
Extra deck monsters add more power and versatility to the deck due to their strength and abilities. Since the extra deck size is limited to 15, you must make wise choices to include the ones you can summon easily and help the deck.
Side deck
All of your side deck cards should counter a deck or more. For example, if you're facing Shaddolls, it'd be wise to side in Shadow-Imprisoning Mirror and Vanity's Emptiness. Side decks are there to help you against a variety of match ups by replacing useless cards in your deck for better ones.
Research
You may be interesting in making a deck but have no idea to how to make it properly. In this case, you have to do some research work. It's not a sin to read on articles, guides or look at decklists to get the gist of how the deck works.
In order to get better at anything, in order to develop your talents, you must fill yourself with knowledge that works. You must research decks similar to yours, talk to people running similar decks, and ask advice of skilled players in the game.
Your goal isn't to copy/net deck, but to take aspects from other strategies to improve your own. A good place to start would be at the Deck Discussion section CLICK HERE!
For a more in depth (but slightly outdated) guide check outs nekojfungs guide here
Last edited by Roach on Mon Dec 14, 2015 6:49 pm; edited 3 times in total
I may not be perfect but mine would be alot more understandable lol 
