This one is not so much a riding skill, but something required when your riding has exceeded your skill or you’ve just got unlucky, the secret is to use your thighs for all the lifting NOT your back.
Ensure the handlebars and front wheel are turned towards the ground.
With your back to the seat grasp the handlebar in one hand and find a secure grip near the rear of the motorcycle.
Using your thigh muscles lift the bike while walking backwards towards it as it rises.
Once upright rest the motorcycle against your butt while changing your grip to secure the motorcycle.