over the years i was very fortunate to have the opportunity to learn from some very good instructors. even after my art education ended i continued to study and practice.
some very important things to always keep in mind are-
-build a good simple understanding of the basics (structure, proportion, perspective, anatomy)
-learn how to break down any form into basic shapes (keep it geometric, keep it simple)
-learn to draw loose (don't be afraid to draw sketchy)
-don't worry if a drawing doesn't come as you'd hoped (it's all just practice)