I know its not te most orthodox combinations, but using hazel or elder for the spindle, and pine for the hearth (yep, just a bit of old palette works well!) is a combination that I regularly use, not least as its readily available. The only thing to look out for is that the pine mustn't be resinous,m or this just forms a gummy lump instead of an ember.
For a handhold, I either use a limpet shell (careful, it'll get hot!) or usually half a small tree branch, split lengthways, cutting a notch for the spindle in the flat side, and using the curved (bark-covered) side for the handhold. For a bow, any bit of curved, dry wood is fine (don't use green wood unless its very stiff, the tension will constantly change as it bends and you'll not get a good rhythm going!
For the string for the bow, I also usually use nylon thread - you want it to be at least 4-5mm thick, or else it will just fray and snap - make sure you don't use a 'plasticky' thread, as this will slip, or a very fibrous one, as this will fray.
Other useful tips:
Make sure the string on the bow is really tight - you want to have to use a bit of effort to get the spindle twisted in, so it grips well enough to prevent slippage (almost all string will stretch/give a bit as you start bowing).
Use the fingers on the hand gripping the bow to tighten the string a bit by pulling the string towards the bow wood, if the tension loosens.
Cut the notch in the board /after/ you've drilled in a nice hole - that way you're getting the ember to fall out at the right point.
Begin at a slowish speed with a lot of pressure - this will generate a lot of dust, and some heat. When you see the hole start to smoke, and the notch is fairly full of black dust you know that there is enough dust to begin to hold a heat - ease off the pressure a little bit, and speed up the strokes - do at least 60 strokes in this speed (in/out = 1 stroke) and you should have a lot of smoke and hopefully a nice ember.
Downward pressure is easiest to obtain if you do the following (if you're left-handed, reverse it):
Put your left foot on the hearth board, to the left of your hole, kneel on your right knee and turn your right foot outwards to balance youself (you should now look a bit like you're kneeling to be knighted!). Put the spindle in the bow, and put this in the hole/handhold. Holding the spindle in your left hand, hold your left elbow tight against your body and run your arm along your left thigh. Your left wrist should 'lock' in by turning your hand a bit to the right, and wedging it in the notch on your shin just below your left kneecap. You should now be able to adjust pressure on the spindle by leaning your whole body weight forwards and backwards, and your arm is fixed to your body, so the force is even and consistent.
At some point I'll try and get a page put up with clear, detailed pics, and maybe some video of the process, as it helps so much more to watch someone actually doing it - body position is key!