Andrew Smith is a 3rd-degree BJJ black belt based out of Richmond, VA (Revolution BJJ). He runs BJJ Path, a video tutorial website.
The "backstep" guard pass sequence in BJJ is extremely valuable to have in your back pocket. If you haven't already reviewed the basics of the backstep pass, you might want to do so before continuing here.
This tutorial will give three fundamentally different ways to get into the position, coming from a passing perspective at first and then using the backstep to get out of a bad situation. One way to approach jiu-jitsu is to try to get pretty good at everything, but the approach I've seen work the best is to try to get to your best positions from the widest range of methods. This is just such an example.
During the Knee Cut Pass
Here's a fantastic way to get into the backstep, and one of the most commonly used today. Start by cutting your right knee across, trying for a classic knee cut guard pass. However, upon near completion, your partner nudges you forward and gets the underhook, meaning that if you continue forward during your current course, you're going to give up your back to your partner.
Drive your weight forward, but at a different angle than your partner is aiming for. Instead, flatten their far shoulder with your hip, helping to keep them flat. Next up, retract your left leg so that you can kick it back and around your partner's legs, without any real chance of them catching your leg during this transition (or taking your back).
This position begins in deep half guard, but you could also be on top of a more conventional half guard. Conceptually, the idea is to step over your partner's head, ultimately ending up in a backstep position. From deep half in particular, if your right leg is trapped, you're going to want to use your right forearm across your partner's neck and jaw area in order to help them look away from you. This makes the stepover portion vastly easier to execute.
From the Back Take Attempt
Another very good time to enter into the backstep position is when your partner is already pulling you into their lap to take your back. Let's assume they already have their right hook in, meaning they are going to be pulling you to the right. As they pull you to the right, once again change the angle slightly. Make sure your shoulders end up on the mat during this transition, not on your partner's stomach. Now it's all about retracting your left leg, very similar to the motion you used to get to the position from the knee cut. Finally, allow your hips to follow your leg as it kicks through, helping to facilitate you ending up on top, sitting on your partner's hips and facing their legs.
Having played around with leglocks far too early on in my own personal jiu-jitsu career (meaning that I strayed heavily from the fundamentals), I've helped my students develop a style that integrates the backstep movement frequently. This can confuse and perplex other white and blue belts. By the time our students get to purple belt, they're so good at the position that it's hard to keep up with their movements.
You can add this into your game almost immediately if you're not already using it, and the variety of different ways I've outlined here may give you some of your own brainstorms. Let the brainstorming happen often and frequently; just don't stray from the fundamentals. As always, let me know how these particular techniques work for you!