This may sound funny but not intended that way at all.
Its best not to let them get there in the first place, it's very difficult to shake a decent pilot off your six one he's planted there.
You have to improve your SA, Situational Awareness, to detect them way before they are on your rear, once a enemy is at your 3 or 9 oclk you should be looking at them and preparing to defend against their attack. Good SA requires your head to always be turning around looking for hazards, similar to driving when you should frequently check your mirrors.
Check the radarmap often at first and look completely around your plane every five seconds or so. In enemy territory when you are expecting an attack, fly in a slight S pattern and look below you at your low 6 to prevent an enemy from sneaking up on you.
Believe it or not a good time to check your 6 is right before you kill someone too. You never know what part of the food chain you'll be and that thing your chasing might be bait for the threat chasing you.
