Graph paper and a pencil. Just pull it out and start drawing, jotting down ideas, and organizing a strategy of executing on the project at hand. Also, Excel (o

Graph paper and a pencil. Just pull it out and start drawing, jotting down ideas, and organizing a strategy of executing on the project at hand. Also, Excel (or other spreadsheet program). Not usually thought of as a tool, but putting small functions in cells and passing inputs/results cell to cell is a good way to start the actual implementation of a solution.