As a new owner of Lightwave, I would recommend getting yourself a copy of Dan Ablan's book, Inside Lightwave. Its a good starting point plus it has a nice little head modelling tutorial which practically holds your hand through each stage.
With regard to your questions - the numbers of polygons you use depends on the modelling technique. With box modelling you will find that you need relatively few polygons to create quite complex objects. The drawback of box modelling is that it takes quite a while to learn and get used to.
How far apart points should be depends on the level of detail you are working to. Bear this in mind though - if you have too many polygons then you will end up having to re-arrange many points just to correct one small area - You have to strike a balance between the detail and the difficulty in altering the mesh. If you have too many points and polygons to deal with, then it becomes really difficult to make corrections to your model as you end up having to pull around many different points to get the model looking just right. There's no real "rule of thumb" as different people have different mesh densities - but you just need to learn how to balance detail in the model with number of polygons you can get away with.
How to know which direction to go - have a look here:
http://www.cgtalk.com/showthread.php?threadid=38469
Hope that helps.