1. Hair traps scents very well, so it's a very good idea to spray on your hairy chest.
2. Doesn't matter. Insides if you want to aim for pulse points, which is often a good idea.
3. Just a preference, not particularly good or bad.
4. On the head/hair also works great since hair traps scents, but you might want to spray at the nape of your neck; not too high up if you want to catch a whiff here and there.
5. Sillage is the amount of fragrance you spread around you; the trail you leave in your wake or in an elevator (for instance).
6. Spray on your naked stomach/chest/back before getting dressed for a subtle prescense and top it off with one or two sprays on the neck/wrists for more direct projection.
Edit: Welcome to BN!