1. You can solve a system of equations using graphs when there are no decimals or fractions in the equations. This can allow you to almost precisely plot a graph, and determine the values of the variables.
2. You can use the substitution method when one (or both) of the equations is already solved for one of the variables.
3. Elimination is best used when the equations are written in the form Ax + B = C, and also when the coefficients are values not equal to 1.