Remember that E is split between two parts- potential and kinetic.
Kinetic (i.e. how fast is this guy? ) Use closure rate to judge.
Potential is a bit different- The straight vanilla answer is altitude=potential energy, but there's more to it then that. Take his a/c type into consideration, and compare it to yours. The differences between them, put in a level environment, will give you a road map to what his strengths/weaknesses are compared to yours. Thus, given equal speeds and altitudes, you may find yourself at an e-disadvantage.
Then, all it is is a matter of getting into his head, and forcing him to fight the fight he can't fight and win.