I also drew like you last time ,with big head and small shoulder .This are tips tokage gave me and I improved.
hm...let's see... something we have in common: the heads are too large. i do it, too, i have this terrible habit of drawing the head too big, so you're not alone. also, the shoulders aren't quite right, you need to make them wider, and unless you're going for the shurgging look, they shouldn't be round on the top like that, your shoulders are more or less straight across (or sloped slightly downward) until they reach the joint where your arm connects. the eyes are a tad wideset, but that might be easily rectified if you adjust the shape of the head a little. you've got no definition to the jawline, add a few angles in there to show the cheekbones and define the chin a little and that should help.
as for drawing the body, one of the things that always helps me is sketching a sort of skeleton before fleshing it out. the body can be divided into 8 more or less equal sections. the first section starts above the body and goes to approximately the temples of the head. the second section from the temples to the shoulder joint. the third from the shoulder to the natural waist; the fourth from the waist to the tops of the thighs. the fifth section from the thighs to just above the knees, the sixth encompasses the knees to just below them, the sevent the lower leg and calf, stopping at the ankles, and the final section is ankles to feet, and you should have about a third of the final section still unused. now, granted, anime proportions are...not always anatomically correct, but i would wait until you have a tru human form down before you start taking stylistic preferences. we must walk before we can run, yes? i also find using a human model helps... i often have my sister pose for me when i can't get a particular positioning right on my own. it's always good to have reference material, even if you do have a handle on the form you're working with.
Hope that helps!