Look how far you've come...
You know what the acronym BMU stands for and how to beat it with a solid engine. You've gotten a pretty good grasp on most of the cards, you read up on strategy on these forums and in a very short time, you've become the focal point of your gaming group when it comes to Dominion. Every time someone from your group manages to beat you, it's celebrated as a common victory for every player, except you of course.
Powered by your newfound self esteem you try your luck on Isotropic because that's where the best players are. And you're already the best player of your gaming group, so it's time to teach those Isotropic noobs a lesson. Surely, they haven't found out about your neat trick with NV and Bridge or when Thief is actually a good buy.
You start to play against fellow low ranked players and it's like taking candy from a baby, sometimes even with the same crying. Slowly, but surely, you work your way up the ladder. That Geronimoo guy (grats on getting first by the way), how tough can he really be? Take away his simulator and you can easily take him on, right? Your level increases quickly and look at that, you're already lvl 20! That sure was easy.
You notice that the best way to advance on the ladder is to play and win against higher ranked opponents, so that's exactly what you're going to do. MrLvl20, taking all comers! Auto-match proposes a match between Lekkit (lvl 34) and you, accept! A few minutes later, you stare at your screen demoralized. GAME OVER. WTF?!? Luckbox! Quickly, another match, Michael Harris, accept! Same result. You're not liking the pattern that's developing, but through your anger you're unable to distill what's really going on and why you are losing.
So why exactly are you losing? What separates a lvl 30+ player from a lvl 20 player? I don't want to write yet another boring strategy article telling you to pay attention to possible trashing options, +Buys, etc.. You know all that already. So what can you do to get past that?
The key difference that I find between myself (lvl ~35) and lvl 20-ish players is end game control. Let me present to you this game:
Example #1: Border Village, Grand Market, Stables. It is apparent from the get go that we are both going to build a sort of engine with those nice action cards. He opens Trade Route, I think that's too slow in the beginning and take Silver instead. We both pick up a Quarry. Through the midgame I regret not buying Trade Route, since I could've used the +Buy. I don't give up, but instead, I start looking for the backdoor. With Stables already gone and Grand Markets and Border Villages low, a 3-pile finish is very likely. I have given him some Curses, so I'm already ahead. It's turn 11 and I start thinking. How many buys does he have? 6, that's enough to clear out the last piles if I buy GMs. What's his economy like? He has only 1 Quarry, I have 2. So he'll probably won't be able to buy up those piles. I buy the GMs I planned to buy and end it on the next turn with my 2 Quarries.
Planning and working your way towards an exit is what you need to do. If you plan and start earlier than your opponent, you will very likely have the advantage.
Another one:
Example #2: Curses, Great Halls and Estates. In this one I start my endgame at turn 20 when I buy an Estate. Due to some Remodeling, Estates were already low. Curses had been flying everywhere, so our economies crumbled. Now, we both could have tried desperately to grab those Provinces, but then the game may have been going 10 turns longer. I discovered an exit, took the first step and my opponent was too late.
So what I'm trying to tell with these examples if that you have to pay very good attention to how the game will likely end and if you can do anything to bend the conditions in your favour. Try to get the advantage by catching your opponent off guard. If he's trying to do the same thing as you, he will likely fail, because you've already planned for it, he hasn't.
Games with just 1 Buy are much easier to manipulate, especially if you're the 2nd player. Also, don't be scared to try something different. A lot of times a player will automatically buy a Duchy if he's behind. For example the score is your opponent 28 VP vs your 24 VP and you're both heavily in the greening stage with the same type decks, you have $6. You could buy a Duchy here, getting to 27 VP, but how does that help you really? He will likely do the same and you will both wittle down the Duchies and after that the Estates until he wins. Sometimes you just have to take a chance. Buy a Gold and hope you can scramble the last Province together or at least one of them.
The best players are just good players with a little more experience so they know what it takes to actually win a game instead of mindlessly grabbing the highest VP card everytime. They know when to switch gears and go for a lame ending or when they have nothing to lose and gamble a bit. Play well, play a lot and you yourself will likely get better at spotting 3-pile endings 10 moves in advance or building that megaturn. Always pay attention to your buys, the piles and of course, your opponent.
Lvl 30+ players: Feel free to interject and comment on what you think separates you from the bunch.