These methods avoid radar

Reduction RCS by design materials, aerodynamics, RAM coating (I call it stealth with physics). EX: F-22, F-35, T-50, B-2, F-117…..

Reduced ability to detect, tracking by radar, with super speed. This was demonstrated by MiG-25 vs SR-71, at now we have MiG-31 and SR-71

http://www.tailsthroughtime.com/2010/11/foxbats-over-sinai.html
https://theaviationist.com/2013/12/04/sr-71-speed-enemy/
http://www.acig.info/CMS/index.php?option=com_content&task=view&id=58&Itemid=62
https://warisboring.com/one-soviet-defector-shoved-japan-into-the-superpower-struggle-953f4df6244f#.jamqpsodf

Jamming detection capabilities, tracking radar by ECM system, jammer pod, DRFM. EX: Su-24/34/35, EA-6B/18G, J-16, JH-7A….

http://www.voltairenet.org/article185860.html
http://www.ausairpower.net/APA-Su-35S-Flanker.html