hm... kinda different from the rosie i owe a nut, but ok, good
edit: there is 3 routes:
1 - the fastest, but the hardest, a lot of discipline and practice on quality anatomy, proportion studies
2 - the slowest but most confortable, keep trying and practice on a leisurable pace, one day you will get it, can take months or can take some years
3 - the "fake", find fine references and copy from them, maybe even using tracing. You will learn something from there, but when you need to draw things without reference will you be like a fish out of the water