Star Battle puzzles always have the same number of stars in each row, column and region (depending on difficulty). So once the required number of stars is filled, any remaining empty cells can be marked with dots to exclude other stars.
To apply this technique, look for any rows, columns or regions that already have enough stars. This will become quite intuitive over time and should be obvious when placing new stars.
In the example, the central star has been placed. As this easy puzzle only requires one star per row and column the remaining cells in the same row and column can be excluded:
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