An overwhelming collection of Sudoku solving strategies for human players is nicely presented and explained on Andrew Stuart's Sudoku page:
**Show Possibles**
1: Hidden Singles
2: Naked Pairs/Triples
3: Hidden Pairs/Triples
4: Naked Quads
5: Pointing Pairs
6: Box/Line Reduction
**Tough Strategies**
7: X-Wing
8: Simple Colouring
9: Y-Wing
10: Sword-Fish
11: XYZ Wing
**Diabolical Strategies**
12: X-Cycles
13: XY-Chain
14: 3D Medusa
15: Jelly-Fish
16: Unique Rectangles
17: Extended Unique Rect.
18: Hidden Unique Rect's
19: WXYZ Wing
20: Aligned Pair Exclusion
**Extreme Strategies**
21: Grouped X-Cycles
22: Empty Rectangles
23: Finned X-Wing
24: Finned Sword-Fish
25: Altern. Inference Chains
26: Sue-de-Coq
27: Digit Forcing Chains
28: Nishio Forcing Chains
29: Cell Forcing Chains
30: Unit Forcing Chains
31: Almost Locked Sets
32: Death Blossom
33: Pattern Overlay Method
34: Quad Forcing Chains
**"Trial and Error"**
35: Bowman's Bingo
As a fairly frequent player, I would judge everything beyond strategy 11 as "no fun anymore". But that is probably a matter of taste.
