For me, being a better player is something like you becoming an expert on a subject. When i started playing magic, i always found myself coming back to a particular archetype (prison). I have since ventured out of that archetype to brew fun stuff, but always came back. My synopsis on how to be a better player is from that mindset, of having "mastered" a deck/archetype.
My goal then was to play this deck into the ground, until i knew it backwards and forwards. Depending on the format, that changed to knowing what my opponents decks are and how they win. Knowledge is power!
After you know your deck, and how it interacts with other decks in the format. you can get a sense of what role to play in your game. Are you the aggressor? or are you controlling until you get your hay-maker/card to get you back in the game? If you have built a deck that you are passionate about (this is especially important in vintage since these cards are an investment!) then you should know what cards you need in any given situation.
PLAY TO YOUR OUTS. if you are on the back foot, or even if you have the advantageous board-state, REMEMBER THIS! Your opponent doesn't want you to win, plan for your opponent to try and stop you, even when you know you have game on board (unless you have information that says otherwise).
I went to Champs 2017 and had the pleasure of meeting a great many people and seeing many different decks being piloted in front of me. I am unfortunately in an area where i have to beg my friends in between modern rounds to grab a proxied vintage deck and jam a game or two before the next round. Between that and using an awesome app to get sample hands (top decked) during down time, all i had to get my knowledge up was listening to EVERY podcast, EVERY youtube video, watching streams when i could, and talking to friends that play legacy and sometimes vintage with me, theorizing about everything i could think of.
Any deck you decide on playing, number one I think is picking a deck you want to win with (of course after evaluating what you think the meta is and what would do well). Knowing the intricacies of your deck vs other decks (triggers, timing, what your opponents spells actually say, oracle text!) Then looking into all the information you can. I would literally go into work listening to Vintage Super league, So many insane plays podcast, Leaving a legacy podcast, anything i could to increase my knowledge of the format.
After that was all said and done, I got ready for EW over the course of two months and came out with a respectable unpowered 6-4 record. I only lost to myself one time that tournament, the rest i blame variance ;-) which unfortunately, is a thing sometimes :-P