When I first started, I simply drew what I wanted, however I wanted. I’d take a few things from different styles I liked and try to draw them in a way that would give me my own style of drawing.
I only started drawing from observation after I realized there was something lacking in my art. No sense of depth, mass, anatomy, etc. I took one session in life drawing, which was basically 10 three hour courses of 30 second to 5 minute poses/gestures from a nude model. It helped me a lot in figuring out how a body moves, the weight and strength put into different poses.
I had to stop after those 10 courses since I didn’t have the funds to continue, but it always helps TONNES to draw from observation.
As for practice, I draw a subject that grabs my eye, that really interests me. That way I’m having fun as I practice. Gesture drawing is always fun as well; it helps you challenge yourself in getting down the pose as quick as possible within the 30 second limit. Hell, sometimes different poses can inspire you to create different characters!