I've played chess casually for years, and my main observation is that no one actually wins if both players are reasonably well matched. The balance tips when a player makes a mistake that leads to them losing. Consequently, the only thing you really need to do to not lose is to make sure you don't make daft blunders, and to recognise when your opponent has. I'm pretty sure it's different at higher levels where people don't make those errors nearly so much, but if you're just starting out, rather than trying to win just remember to not screw up.
1200-1300 is about the rating where players stop making blunders to such a grand scale. Also, at that rating, blunders start to get punished much more heavily. Before 1200, it really is all about learning to stop blundering. At GM level though, they're gaining advantages at minuscule levels, until it leads to some "big" breakthrough, which they can continue to exploit.
At some points you'll move from mistake vs correct play to finding imbalances. Most things aren't really mistakes but contain advantages and disadvantages. Matching all these imbalances together to a strategy and at the same time disturbing the opponent from putting his imbalances into synergies, that's what expert games are about (or at least higher advanced level, I can't say I really understand expert level).
