Star Battle technique: neighbor squeeze
Pretend a star sits in a cell.
A star blocks its row, column, region and all eight neighbours. A neighbor squeeze asks what a star in one candidate cell would take away. If placing it would remove every remaining possibility of some other unit, the cell cannot hold a star, so you cross it out.
How to spot it
Look at units that have just two or three candidate cells left, especially ones squeezed into a corner. Check whether a single tempting cell touches all of those candidates. If it does, it is out.
Example
Example from a real Pencilmark puzzle (#38, 6×6). Solver explanation: “A star at row 1, column 5 would rule out every remaining cell of region 1. So that cell cannot hold a star.”
This is a one-step trial, not guessing: you only reject a cell if the contradiction is immediate.