The fact it is ASK makes your life slightly easier, but you will still need to know the exact frequency. Some transmitters can be programmed to use a certain frequency from a small range around the 433Mhz band, some are set to a constant frequency.
You should be able to get some basic information by hooking a uC to a receiver and observing what comes out. I have used the PICKit2 as a basic logic analyser for this before, but a decent logic analyser would go a long way.
How much control do you have over the transmitter? Can you make it transmit when you want? Is it a black box you have no control of? Or are you trying to reverse engineer transmissions when you don't even know much about the transmitter?
Be warned that the 433Mhz band can be pretty noisy. Even with decent power supply filtering I could pickup all sorts of things with my little receiver.
I couldn't find any information about the "2226 protocol", can you elaborate?