Practise the Naked Single

A cell with only one candidate left.

8 real positions, each taken from an actual puzzle at the moment this was the cheapest move available. Two steps: find the cells that form the pattern, then find the candidate it rules out. A near miss tells you how many you had right, so getting it wrong is worth something.

Select the cells that form the pattern, then check. 1 / 8

6	1	7	4	249	3	8	5	249
4	38	58	1	259	6	379	379	239
39	29	25	7	8	45	13	14	6
78	45	3	9	457	1	2	6	58
179	29	12	3	6	58	4	79	58
789	45	6	458	457	2	379	379	1
5	36	4	2	13	7	1369	8	39
13	7	18	4568	45	9	36	2	34
2	368	9	68	13	48	5	14	7

How to spot it

If you keep pencil marks, look for a cell with a single mark. If you do not, check cells at the intersection of busy rows, columns and boxes — a cell whose three houses are well filled has few candidates left.

Full explanation on the Naked Single reference page.

Practise something else

Hidden Single A digit with only one home left in a house, even though that cell has other candidates.
Naked Pair Two cells in a house holding the same two candidates lock those digits away from the rest.