Have a search as this is a topic that gets discussed a lot, especially around this time of year.
Different people like to go to different lengths, if you are new to it then it might pay to (actually) pay to have someone do it for you but watch and learn what/how. There might be a RIB.netter nearby for this and the payment might end up being in liquid form.
It is also often does as a two stage process, ie winterise the engine now for storage and then decommission it in spring. For example I cant see the point in changing spark plugs now when they are just going to sit around for a couple of months - do that at the start of the season.
Anyway, like I say it is a variable beast so have a search through similar threads!