stretch, stretch & stretch, lots of Hot showers while doing stretching, yoga exercises. This is not something you just do. You take risk of injury if you are impatient. I had some PDF I can send, but will have to find them. After becoming limber & relaxed, do as much stretching as possible. Then gradually curl your body over by laying on bed with your head propted up with 2 pillows, place 1 pillow under your hips, curl over your head and place your feet behind your head. Relax and breath, relaxation is key. Gradually pull your grown and head towards one another and place the head of your cock in your mouth or atempt to lick the precum.
Another way is after stretching extremely well in a Hot shower and have been stretching for a while prior. Sit on the Toliet and place your forearms under and through your thighs, while doing so, bend your head into your lap and interlock your hands behind your head. I have got to the point I could get several inches in my mouth, but never had a camera while doing so. Sorry