A few tips....
1) Learn to roll at high alpha with the rudder.
2) Practice your deflection shooting. You'd be surprised how often a MiG-17 screws up and crosses your flight path well within gun range.
3) When in a scissors, remember tip 1, and don't overcompensate. It only takes me 2-3 scissors before I go from having a MiG-21 on my six, to being on his six.
4) Use lag pursuit. Force your opponent to execute large, energy-bleeding maneuvers, but don't follow his lead!
5) Use clouds to force an opponent to lose track of you. Estimate where he'll be when you both emerge (from the clouds), and try to be on his six.
6) Only use the vertical when you know that your aircraft's still in a high energy state, but your opponent's is not.