While you can try to deduce notes from reading about the individual notes, reading reviews and then searching for the notes in the fragrance, or finding two fragrances that both share a note and trying to see what they have in common, this is a haphazard approach at best. Especially with regards to reviews - it's often a case of the blind leading the blind. Most people simply don't know what guaiac wood smells like, for instance. I don't blame them - it's still VERY difficult, and sometimes impossible - to tease apart the components of a scent even when you do know what the various ingredients smell like. Besides, there are molecules out there that you simply won't have access to unless you are a perfumer for a big company - so you'll never learn what they smell like in isolation.
I've got experience with a few synthetic aroma chemicals and about 200 natural materials. Really, the only way to really learn the notes is to experience them in isolation. I'd suggest a beginner's kit from Perfumer's Apprentice if you're serious about it. Otherwise - or rather, regardless - you can learn certain notes such as many spices from the spices you can buy at the store. (Note, however, that the synthetics, and natural essential oils and absolutes and C02 extracts often smell different than the fresh/dried spice.)
Flowers, too, you can sniff fairly easily. Head to a local gardening store/greenhouse and sniff away!