I’ve been trying to hit the Osoto Gari since the day I learned it and find it quite difficult to set up and maintain the elbow/bicep grip as well as the collar tie/collar grip. They usually step back with their legs, lowering their upper body, which makes it hard for me to step to their side and start sweeping.
The tip I learned today is to set up the Osoto Gari; you need to pay attention to their foot placement. One foot must be placed forward so you can align it with your feet. From there, you can quickly switch your grip to their arm and neck. To achieve this foot placement, you can push and pull, as well as pulling them sideways or in a circle. Once their feet are in place, you can start by setting up your grips and move into the Osoto Gari. Remember to pull them toward you when initiating the sweep. Utilize your collar grip when in Gi—pull the collar up and punch them toward you, hitting your shoulder with theirs while also pulling their arm. Bring your outside arm up and out, look at your wristwatch, swing your leg, and kick back, chopping down on their inner knee.
If you get taken down from the Osoto Gari (or any takedown, for that matter), remember to relax and break your fall in time and properly. Slap your arm to the ground to cancel the force, quickly roll onto your shoulder away from them, and either escape or pull them into your guard.