It's no secret really.
Ask any older player what it takes and invariably you boil down to 3 things:
USE YOUR TIME
THINK CHECKS, CAPTURES & THREATS
Somehow I find the chief failings of our young players (based on my observations at the recent Serangoon Inter-team tournament) is that their level of concentration is generally lower to that of the older players. When a player concentrates, he starts to work out relationships between his pieces and his opponents. He will be aware of what can happen when one of his pieces leaves a square, which can be occupied by his opponent if there is insufficient control of it.
I am guilty of this in my first game whereby I lost a Queen, so really it can happen to anyone. No excuses! I could have paid dearly for it but I was lucky. That lesson woke me up real fast and for the remaining games I concentrated hard for every game and it was amazing how much the mind's eye can see once in that mode. I didn't waste any time working out my moves, although I must say my intuition was on form that weekend and allowed me to quickly pick the best moves on the board. Well, it did falter towards the end when tiredness crept in. Other than that, I generally played up to my expectations.
My opponents generally did not play their best moves, much a times I was surprises that they often did not follow the thread of the game and surprised me with their responses. It was as if I was doing my thing and they did theirs, only to be rudely shocked when loss of material or mate stared at their faces. Here I am convinced that many simply do not ask themselves what I was doing with my move, whereas I could not understand what they were doing in the light of my threats. So converting the wins was simple.
If there is anything to learn from our games, I think, its simply this: If you don't think your opponent opposite you is trying to win the game and pay no attention to his moves, then be ready to face defeat again and again until you wake up. This advice goes to my students, especially those who have lost badly. To get better, one must learn to question what went wrong and be up to facing the lessons to be learnt. Otherwise, playing tournament after tournament does nothing to help - only to perfect your "mistakes".