The key for me (after mucho
The key for me (after mucho blisters) was to relax my feet totally and lean slightly forward from the ankles. I'm taking a stab here at describing the "form" we've all been referring to. Finally getting my "form" right, which was really just relaxing and leaning forward with good posture of the back and upper body, got me to increase distance, but only after the sole (plantar) skin thickened up a bit with alternating days on/off BFR very short distances. Leaning forward from your waist rather than your ankles is not your friend and will not help.
To get what this "leaning from the ankles" feels like, stand about 2 feet from a wall, facing the wall, with excellent upright posture. Put your hands on the wall and, maintaining your excellent upright posture, lean forward without moving your feet at all. You do this by bending your elbows slightly. As you will notice, were you to suddenly remove your hands, you would hit the wall with your face. While I do not wholeheartedly recommend testing the results of this theoretical process for more than a couple of milliseconds followed by immediate replacement of the hands on the wall, it will give you the feeling for what "the BF lean" feels like.
Unlike traditional running, you are not launching yourself forward muscularly, essentially jumping forward. Instead, gravity and your lean forward provides your forward motion, while your cleanly and smoothly lifting and placing your feet keeps you from the infamous face plant. The degree of lean largely determines the speed of forward motion (there are other factors, but save those for later).
I hope this helps detail some of the great advice everyone has been providing already. We've all been there and would love to help you avoid the pitfalls we've so thoughtfully but painfully already discovered.