Last but not least I don't understand why there are so many different tutorials on the webz. You can find nearly everything you need to use aircrack-ng directly on there site and in my opinion these are the best tutorials you will find
Finally, someone with the same opinion as mine. Aircrack-ng's website is full of documentation, I learned mostly everything I know about wireless attacks there, and I would say I've gained a fairly good knowledge when compared with some tutorials where the author limits himself to copy paste commands and tell you "put the ssid here, the bssid there and hit enter".
Also, in order to obtain some more knowledge, I would advise people to see what's happening behind the curtains (wireshark). It helps a lot to understand what's really happening.