1. Modeling Algorithm Draw a picture Schematic
Sufficient detail to capture important features
Label directions of motion

2. Modeling Algorithm Draw appropriate free body diagrams
One for each independent body or degree of freedom
Draw and label all forces (guess at a direction of action)
Label direction of motion

3. Modeling Algorithm Write constitutive equations
For each force in free body diagrams
With appropriate directions
Action and re-action forces in opposite directions

4. Modeling Algorithm Write conservation equations Momentum Energy Mass
Volume
Charge
Concentration
etc

5. Modeling Algorithm Rearrange conservation equations
Use substitutions from constitutive relations
Monic form
So as to see:
patterns
relationships
influences