The more you fly, the more that 'E' becomes a tangible factor in your decision making. You eventually get to a point where calculations of relative E between you and enemy are constantly ongoing. There is a critical point, you can probably break it down into the split second realm, during a fight when you are assured of two things:
a) You can, through E bleeding manuevering of your own or due to natural state of the engagement, or due to angles, force your enemy out in front of you
b) You can, after the above happens, quickly vector back to your previous (and your enemy's) flight path
Parts A and B must happen together, as A alone will simply force a restart of the fight, with you now the worse off having lost more E, and Part B alone...well that is where the majority of new players end up, with a bogey on their six that they are unable to shake regardless of changing vector.
Now there is an ever important Part C, which is
c) After vectoring back onto the enemy's flight path, you know that you will have the E to stay close enough to force his evasive manuevering or E loss of his own
The good pilots can force parts A and B, the great pilots know that parts A, B, and C will be successful before they even initiate part A.
It's all about practice, experience, and that sort of thing.
Sorry I can't explain the manuevers in more detail (they are very very situation specific, so generalities won't help much), but I'm sure a trainer or someone with more experience than me can explain it better.