Excellent tutorial, Amphirion! Photography is awesome, though it is often extremely frustrating for newbies, which can make them give up on trying to improve their technique. Your tutorial keeps things simple enough that the info is usable to everyone, whether they have a DSLR or are just starting out with their first compact camera.
One aspect I differ on is the use of flash... When a flash is used correctly, you won't be able to tell if the shot was done in natural or artificial lighting, which is my personal goal when shooting. IMO, flash is helpful or even necessary in many situations in order to get a satisfactory shot. For example, if you are shooting an outdoor plant in bright sunlight, it is usually better to use flash. Although this seems paradoxical, bright sunlight creates ugly, extremely harsh shadows, and the flash will help fill those in a bit, like here:
Also, using a flash for macro photography (namely true macro photography with a 1:1 scale) is imperative in order to be able to use an aperture small enough to get a significant portion of the subject in focus. Yeah, f/2.8 can look cool when you want to get all artsy fartsy, but when you
really want to show off the subject, you need a better depth of field:
Flash is also useful for crappy indoor lighting too, especially if it's someplace where you can't control the amount of ambient light (like an orchid exposition):
In short: Don't fear the flash! It can really help out when used in conjunction with other sources of light. Also ISO... Don't be afraid of bumping up the ISO if it means you can get a much better shot lighting- and composition-wise. Unless you're going to be making large prints of your photos, no one will notice that you're shooting with 800 ISO instead of 200.