first thing
get a light meter stat..otherwise your gonna spend all day from trial and error getting a correct exposure..and your camere view screen will play tricks with you.
Shit you'll deal with w/o a lightmeter..

overexposed/finding what looks right even when your still off.
:metered and shot lighted correctly the first time/minus the de-saturation, but im sure u get the idea..

its saves ya a great headache and not having to deal with photoshop to fix your exposures
2nd. if u have the software..shoot tethered.so u know EXACTLY what your producing..hell.i'll even get it for you if you want it
i'll write ya up some examples for you tomorrow and show u some more examples of lighting like i did on Ran in the studio a few days ago. it mainly depends what kind of light u want,(like your subject harsh lit or soft lit) or what effect your looking for. if your really serious about portraits, i also recommend tracking down a softbox also.
for starters, one thing that will help you is the inverse square law.Next time i do something in the studio, i'll invite ya up if want to check it out firsthand.
he inverse square law says is that an object that is twice the distance from a point source of light will receive a quarter of the illumination. So what it means to us photographers is that if you move your subject from 3 metres away to six metres away, you will need four times the amount of light for the same exposure. This can most easily be achieved by opening the lens aperture two f-stops or using a flash that is four times as powerful
light diminishes so rapidly because it spreads and so a smaller and smaller proportion of the light hits the object
i can honestly say that your progressing faster than any other up and coming guys that are new to the dslr world...
keep up the good work
if u have any questions, pm me..i'll more than happy to help ya dude