Practice
Hard technique
Naked Pair
Two cells in a unit with the same two candidates hold those two digits. Rule them out of the rest of the unit.
1FocusOnly what mattersNext
Start2Notes givenFull grid, notes filled inLocked
3Your own notesFull grid, you make the notesLocked
4Against the clockHow many in a row?Locked
5 right in a row passes a level