Clinching. Clinching is one of the most important aspects in the grappling arts - regardless of your style or ruleset. Some styles dominate in the clinch, while others are scared to engage in it. Whether you are a sport grappler or just know some basics for self defense, clinch fighting is one the most important areas you can train.
Wrestlers and Judokas/Sambists have no problem clinching up, finding a weakness in their opponent and then exploiting it. BJJ players pretty much avoid it all together and try to establish control on the legs or torso. One martial art that gets very little credit for their hard nosed, yet very technical clinching, is Muay Thai. The clinch in used in traditional Muay Thai to wear an opponent down, setup throws and sweep and also knees and elbows. A Muay Thai specialist has an almost upright posture with strong emphasis on having their hips set in front of their spine and their head up. A posture that almost mimics old school Judo's upright clinching and grip fighting. If you haven't had the opportunity to personally train 1v1 with a high-level kickboxer, we suggest you do. And if you just happen to be a grappler, even more of a reason to do so. There is no doubt how valuable this particular style is and it can add a new aspect of in-fighting that might surprise your opponents.
Check out the Ruskies from Blood & Sweat Russia and there clinch tutorial at Combat Muay Thai Moscow.