Over the last nineteen years I have played a lot of deck construction games (call them Collectible Card Games, Trading Card Games or Living Card Games) in the last nineteen years. Each game has its own unique elements to consider when constructing a deck for it. For example, in Magic: The Gathering it is the land/mana base that play with, in Doomtown it is the card suits and values you play with and what poker hands those cards will make, in 7th Sea it is the attack types on the cards, in Game of Thrones it is the challenge icons that you are playing with, in Call of Cthulhu it is which struggle icons you play with, and so on. In all though, the process of deckbuilding itself is similar. You start with an idea, you look at what cards you can implement that idea with (or sometimes which cards you can flesh it out with), put it together, edit it down and then play with it and revise it until moving on to the next deck and repeating the process.
Like everything else, the more you do of something, the easier it becomes. Things connect in your brain in new ways. With these games, the more variety you are exposed to, the more ways that cards work together or against eachother you become aware of. Much of this is summed up in the concept of the metagame, the game within the game, adapting to your current play environment.
When I first started playing Magic: The Gathering the way my friends and I constructed decks was to throw all of our cards of certain colours together, throw in a bunch of appropriate land and play. We had great fun, but had no idea about how to contruct decks. I remember the first really focused, constructed deck that I played against. It was a mono-blue deck with Merfolk of the Pearl Trident, Clone, Vesuvan Doppelganger and Leviathan. Keep in mind I was probably playing with a set of random black-blue cards and my deck was about 100 cards. I was slaughtered. What I remembered though is how everything in the opposing deck worked together. Two swings from Leviathan (a 10/10 trampler) was prettymuch all one needed to win, so the cost of sacking two islands a turn to it was nothing. Flash forward another year when my step-brother visited from out of town, bringing to my usual playgroup a blue-black-white deck. It was just after Ice Age had been released and the deck had Merieke Ri Berit and Norritt. Most of us had moved away from random assortments of cards of the same colours by this point, but all of our games were Mickey Mouse, in that we didn't actively attack eachother for the first half of the game while we built up forces, then one player would launch an attack and we would deal with him or her, then build up until another player tried attacking. Needless to say, my step-brother beat us soundly.
Another number of years passed. My deck construction skills improved, as did those of my fellow players. Then one of my friends bought copies of the World Championship decks for Magic. My mind was blown. I had sworn off counterspell decks because I had felt they were too unfair. What's the fun in every spell you try playing countered by your opponent? However, one of the decks had counterspells and didn't play them unfairly. The counterspells were there to gain time to build up to the heavy hitters. Previously each of us who played together had our own focus of deck types -- red-green aggro, white control/life-gain, and so on -- but being exposed to these different decks opened up the possibilities. I began truly understanding that certain cards were better to play with than others. A good part of this is came from our collections growing over time, so that the choices of what cards we had to play with become less restrictive.
Since then I have become much better at deck construction, building a multitide of decks for a many different games. While I am not constructing decks regularly anymore, I remain facinated by deck construction in the multitude of games that I keep track of. When I do have a chance to think about deck construction, I am often faced with decks that are begging to be made. The component pieces clearly line up because they are thematically linked (ghouls in one of the recent cycles in Call of Cthulhu for instance) or specifically name eachother (like a few cycles of cards in M11). I prefer to give my attention to the decks that are a little quieter though, the ones that come while flipping through a pack of cards and make you look a card from another pack I looked at previously. While it's easy to put together the obvious decks, and is often a good way to put together teaching decks or good thematic decks, my favourite decks are the quieter ones. The ones that take form in moments of inspiration or realization. These decks often don't work to win, some of my favourite Magic decks have been like Rube Goldberg machines, but sometimes they do, and in both cases the result is fun.