The short answer: on a 3×3 board you cannot beat an attentive opponent — with perfect play from both sides the game always ends in a draw. Wins come from mistakes, and to avoid making them yourself you only need four things: the value of the first move, what a fork is (a move that leaves you two ways to complete a line at once — the opponent cannot block both), the order in which to claim squares, and how bigger boards differ.
No. The 3×3 board is solved: if neither player errs, the game ends in a draw. A win is only possible after the opponent makes a mistake, so the goal of strong play is to never lose and to punish slips.
The centre: four of the eight winning lines run through it, against three through a corner and only two through an edge square. If the opponent takes the centre first, the best reply is a corner.
A move that creates two threats to complete a line at once. Your opponent cannot block both with one move, so you win on the next one. Nearly every win in tic tac toe looks exactly like this.
Play a corner. Answering on an edge loses: it lets the opponent build a fork. After that, stick to the rule "complete your own line first, block theirs second".
Bigger boards need four in a row, and the key shape is an open three: three of your marks in a row with an empty square at both ends. It cannot be blocked in one move, so it is as good as a win — and the opponent's threes must be cut before they become open.