Solution Techniques
Solving basic Hadoku is not very different from Sudoku. If an area has just a single empty field, fill in the missing number. If it has multiple missing fields try to eliminate possibilities by looking at neighboring fields. If a field is down to a single possibility, fill it.
Below is the complete list of more advanced solving techniques.
Intermediate Solution Techniques
Arrow - Hidden Subset - Triangle
Advanced Solution Techniques
Box - Linked Pair - Unique Solution - Cycle Contradiction - Chain Contradiction