The center keeps more directions open
A stone near the center has room to grow horizontally, vertically and on both diagonals. Edge play is possible, but it gives the opponent fewer directions to monitor.
Do not pack every early stone into one straight line. An offset stone or a one-cell gap can belong to several later patterns. Ask before each move: after the obvious block, do I still have a meaningful continuation?
Rank threats before acting
Handle an immediate five first, then a four, followed by open or multi-directional threes. An open three can grow at both ends; a closed three is far less forcing.
Evaluate every shape together with its free continuation cells. The edge and opposing stones are permanent blocks. A visible line may not be urgent when it has only one continuation and a stronger threat exists elsewhere.
A fork creates two threats with one move
A fork occurs when one stone creates two forcing continuations. The opponent can close only one branch with a single move. Look for empty cells where two of your developing patterns intersect.
Defend by applying the same logic backwards. Do not wait until two finished threats are visible. Occupy the shared key cell or create a stronger forcing move before the fork forms.
Good defense also builds your plan
When several blocks work, choose one connected to your stones or one that removes a second opposing direction. It becomes a move that can recover initiative instead of merely surviving.
Do not continue your attack automatically. First inspect every opposing line and broken pattern. Many losses come not from choosing the wrong block but from never comparing the urgency of both players threats.