use largish apertures for hand held so you get high speed
if you use a tripod then you can do some smaller apertures
get the eyes sharp
not the background
place the sitter well away from the background and if you can use around 100mm lens length
dont get shadows under the eyes ...a small one under the nose is ok
and try to use some side lighting for modelling
if its a lady shot you may not want it too sharp
and take some form of reflector to lighten any shadows
dont have the sitter looking into a bright light source as they will screw the eyes up
get catchlights in the eyes
if using flash try to soften it with diffusion or bounce it indoors off a white surface
lots more i am sure which others can advise
i dont take much portraits but do like to observe the above
welcome and lots of luck
ps..its good to know your sitter to get the 'wall' down..this is my younger sister..i am experimenting with black to white from colour...i dont think my camera has a b/w setting..
