The strongest techniques in number logic puzzles are usually not isolated tricks. They are habits that keep your candidate model accurate while information changes across the grid.
Track missing sets
Instead of asking “what goes here?”, ask “which digits are missing from this row?” and “which are missing from this column?”. Intersect those answers with the cage.
Prefer forced groups
A group of two cells that can only contain two specific digits is useful even before you know their exact order. Those digits can be excluded from other cells in the same line.
Use contradiction as verification, not guessing
If a proposed candidate immediately makes a row, column or cage impossible, eliminate it. The important distinction is that the contradiction should follow directly from visible constraints, not from a long speculative branch.
Recalculate after placements
Candidate notes become stale quickly. Every committed digit should trigger a short row-column-cage rescan.
Put the idea into practice
The fastest way to understand the interaction between row, column and cage constraints is to solve a board. Start with the free practice puzzle, then enter the live world when you are ready to race for Discoverer.