In quality improvement some of the tools one might use are:

Tools for mapping processes

Flowcharts
Work flow diagram
Value added flowchart

Tools for ideas generation and seeing connections

Cause and effect diagram
Brainstorming
Relations diagram

Tools for data collection and analysis

Histogram
Scattergram
Control chart
Pareto analysis
Run charts

Examples

Examples of these and many other tools are in:

Quality management tools and techniques: an overview. B.G. Dale, H.S. Bunney and P. Shaw. Chapter 17 in Managing Quality ed by Barrie G. Dale Prentice Hall

Keeping Track: Measurements of Improvement, Progress and Success. Chapter 7 in The Leaders Handbook, A Guide to Inspiring your people and managing the daily workflow. Peter R Scholtes. McGraw Hill 1998

The Six Sigma Way Team Fieldbook. An implementation guide for process improvement teams. 2002. Peter S Pande, Robert P. Neuman and Roland R. Cavanagh. McGraw-Hill