I quote from Pavel:

“The SWING is the foundation of of effective Russian kettlebell training. It requires hip thrust, compressed breathing, rooting, “wedging,” and  in the summation of efforts, skills essential to many other kettlebell drills, as well military, martial and athletic applications. The swing maximizes muscular endurance of the back and waist. These are critical factors for lower back pain prevention. The swing is a a powerful body strength builder and the cornerstone of effective conditioning. Although apparently simple, it is not easy and it is the ‘Sanchin kata’ of kettlebell training. As one Army Special Forces operator put it after an RKC course, ‘A swing is not just a swing.’  Do swings (correctly) and do them often.”

If you want to increase your level of strength and conditioning than the two handed swing can and should be a staple of your training. It needs to be performed “Hard Style.”

The RKC Hardstyle swing is about maximum tension at the top, projection of force forward and explosive, crisp hip drive.Ironically, you may find that as  your hardstyle swing technique improves you will not be able to perform as many reps as each rep will become harder and you will be generating muscular tension at the top and bottom of each rep. The result is a more brutal and efficient workout. You will get better results from less reps. Less will become more.
Do not let your shoulder come out at the top of the swing. Retract your shoulder (suck it in) especially at the top of the swing. This activates the lats.

Stay tight and keep your chest squared parallel to the facing wall. This activates the obliques.

Do not drive your knees forward. Keep your shins vertical on the assisted kettlebell ascent and drive back with your hips. This is safer on your knees and lower back.

The hardstyle swing is about projection of force forward, not upward. Imagine your hip drive throwing the kettlebell forward toward the facing wall, not up toward the ceiling. IF you swing too high it is very difficult to not put pressure on your lumbar spine.
Keep your knees locked at the top of the swing. At the top of the swing your body should form two straight lines. One vertical line from your feet to the top of your head and one straight line from your shoulders to the kettlebell.

Recruit  tension in your abs and glutes at the top of the swing. Build maximum tension at the top as if you are trying to freeze the kettlebell at the top of swing. Pinch a proverbial coin between your butt cheeks.

Do not be passive and let gravity pull the kettlebell downward for you. Aggressively hike pass the kettlebell backward on the downswing. This will force you to perform the next rep against a kettlebell that has been accelerated faster than gravity would allow.

Any RKC will have the tools and corrective drills necessary to help you squeeze the most out of your technique.