Andrew Smith is a 3rd-degree BJJ black belt based out of Richmond, VA (Revolution BJJ). He runs BJJ Path, a video tutorial website.
X-guard is the best guard. Well, that's a little subjective, but it's a position that more often than not leads to a sweep. Once you're in the position, the sweeps are relatively easy to hit. Getting there, on the other hand, can be a real challenge, particularly if your opponent is savvy and understands how bad things can be for them if you get underneath them. Here, we'll cover a relatively basic entry you can use right away, then augment this with considerably more advanced techniques you can use to sneak into X-guard on virtually any partner.
Start with a basic butterfly guard position. While you try to sweep your partner to your right, they stand up, making the basic butterfly sweep all but impossible. This is the ideal time to enter into X-guard. Leading with your right arm, dive deep underneath your partner, not stopping until you are facing your left, fully under your partner's hips. Keep your butterfly hook exactly where it is, behind your partner's knee (you can start at the thigh and then slide down a little to the knee, but don't remove it!). Meanwhile, hug their knee with your right arm. My preferred grip here is to hug tightly above their kneecap, using my neck to pinch their foot and ankle in place, so they can't simply step away or over. Next, you need to insert your second hook from behind, making sure your foot ends up across your partner's hip, as though they are putting your leg away into their pants pocket. From here, a stand in base sweep is ultra simple.
Getting the Second Foot There
Sometimes, it can be tough to get that second hook in, so you can just move your hips further to their back. Here, use a circle/pendulum motion to utilize momentum to get fully onto your left hip, facing forward. This will allow plenty of room for your foot to make its way underneath your partner's hips, ending up hooking tight to their hip. Think "live toes" while you're doing this (curling your toes toward you by flexing your foot).
Deep Half Wizardry
This is a much more advanced entry into X-guard, but with a little practice, you can get there on amazing practitioners. Start by swinging into deep half guard with a hook, and make a move to a "two on one" position (two legs on their one—your shin should be inside of the crook of their knee; once again, your butterfly hook doesn't really move from low down on their ankle at first). Instead of finishing the entry into deep half, change direction by framing off of your partner's hip, then shoot your left leg through to the other side of your partner, ending up behind them. Reach your left arm through, in between your legs. Instead of going straight to X-guard, which will likely be all but impossible, transition to single leg X-guard first. From here, you can make space by pushing, then get your second hook in. You can opt for a modified X-guard instead of crossing your foot all the way over to your partner's other hip, too.
Another use for modified X-guard arises during the waiter sweep, whenever you can't simply get your partner to go over. This transition to X-guard is sneaky and effective, although it does require a minimum baseline of flexibility. The key is to elevate your partner's leg as high as possible, grabbing the pants and pushing up. The video more or less speaks for itself, but the move does require a thorough knowledge of both deep half guard and the waiter sweep position.
As you can no doubt see, the entries into X-guard are as diverse as any other type of position in jiu jitsu. There are simple, effective ways to get there, and there are very sneaky methods for when those fail (or for when you just plain feel fancy). Work on the fundamental stuff first, and once you understand it and get good at a few basic sweeps, try some of the trickier stuff. As always, let me know how it's working for you!