When you can't see a fork, you've never drilled enough forks. Each set serves up puzzles in a single tactical theme - mate-in-1, pin, skewer, sacrifice, whatever. Solve until the pattern lives in your fingers.
How it works. Pick a theme. Solve puzzles in that theme one after another. Wrong moves don't end the streak - just keep going. Switch themes anytime.
Why it works. Mixed-theme puzzle solving builds general skill. Single-theme drilling builds recognition - the moment you see the position, the answer is already in your head.