The system is the same everywhere. Since you asked for a step by step guide, here goes (simplifying madly!)...
First, they work out which children have applied for each school. They all go on the list regardless of whether they have made the school their first choice or their last choice.
Next the children applying for each school are placed in order based on the admission criteria for that school. For LA schools this is done by the LA. For academies, foundation schools and most faith schools it is done by the school. Note that there are strict limits on what information can be used for this ranking and it is done ONLY on the grounds stated in the admission criteria.
Now, for each school you draw a line after the admission number. The children above that line have a place at that school.
At this point there will be some children with places at more than one school. This is where preferences come into play. If the child has places at, say, their 2nd and 4th preference schools they will get the place at their 2nd preference. This, of course, frees up a place in their 4th preference school which goes to the next child on the list. You deal with all children with multiple places this way and keep going until no child has more than one place.
Finally you look at the children who don't have a place. They will usually be admitted to the nearest available school with places.
I have missed out loads of stuff including the complications caused by people from within the borough applying for schools in other boroughs and people outside the borough applying for schools in this borough. But hopefully that is enough to give some idea of how the process works.
The simple summary of all that is that there is no point trying to game the system. You simply put your preferred schools in order of preference. The whole idea of equal preference (as this system is known) is to make it easy for you to decide what order to put your choices in, without worrying about whether putting a particular school as 2nd choice might mean you won't get in to it. I would, however, echo the advice that you should make your last choice an unpopular school that you consider acceptable. That way you have a good chance of ending up there if all else fails, rather than any less acceptable school the council might allocate if you don't get a place at any of your choices.
