if you want my advice, this is the drill i give my *students*, note that i ain't speaking about cartoons, cool drawings, anime characters, etc. i'm talking about real life drawing.
start with hands in the first week, then get to pieces of clothing in the second, then random people, then hands again, and i mean real life drawing.
try to be quick, do your drawings in 5 to 3 minutes, but don't overlook things, try to be as acurate as possible without using an eraser or re-doing anything, corrections have no place in exercises.
if you're aiming for a realistic drawing you should try at all costs to NOT apply memorized drawings or symbols, so avoid drawing eyes, noses and mouths, draw mainly stuff that you can't identify. if you're drawing an entire person don't draw any features of it's face or it's fingers, instead, try to catch the shape they form instead of thinking of them as fingers and eyes and noses.
Something important to look at are negative spaces. For example, when drawing your hand, drawing the space between your fingers with accuracy is as important as drawing the fingers themselves, and, as this space is merely a space, you can use it often to escape your preconceptions. We all have preconceptions: subconsciously, we all think we know how wide a finger is compared to it's length, and we are all wrong at variable levels, but we don't have as many preconceptions about the triangle the empty space between your fingers forms, so trying to draw this may be more fruitful. Post a few pictures of your drawings and your models(your hands) and we'll give you some advice.