There are a few ways to enter the different events, here are some examples.
These normally involve a computer and sometimes free goodies for the first few entries, generally reserved for the forward planning organized runners.
These entries usually have an extra charge but work for the “decide on the day” runners. Decisions can be based on weather, mood or a “how bad is your hangover” barometer.
Generally reserved for the male species, these entries involve a few friends, several beers and a lot of bravado and back slapping. Once you have entered under these circumstances it is very difficult to pull out and despite a complete lack of training, preparation and foward thinking you will find yourself on the start line not really at all sure how you got there in the first place. On a side note this is also why men generally pay higher insurance premiums.
So if you happen to be in a pub with a few running friends be very, very careful and do not commit to anything no matter how good an idea it seems at the time.