Every LA will publish on their website the admission arrangements for all the schools in their local authority. Plus many nurseries and the schools have copies, but timing is everything.
You need to look carefully at the admission arrangements for each of the schools that you are interested in, as they can vary depending on the type of school - for instance church schools will frequently have some kind of priority for pupils/ parents who attend school.
There is a cut off date for the form to be completed, which is usually sometime in December or January. It does not matter when you think your child might start in school, if they are starting anytime from September 2011 to August 2012 you need to apply by the cutoff date specified. If you do not apply before the cutoff date then there is a high likelyhood that you will not get any of your preferences.
Before you apply go to all the schools - many primaries do not have a set open day, you just need to make arrangements to go in and have a look around. I would always look for schools that have a bit of buzz about the palce, wehre there are lots of things on the wall and the pupils seem involved and working. I would always be happier if it is the head or deputy head showing me around and answering questions and I would definitely be put off by them not letting you into some or all of the classrooms. Look at Ofsted reports but be aware that thinsg do change in schools, so anything more than 12 months ago may not be valid.
When you fill in your preference form you need to make sure that you put down 3 preferences. Make sure they are sensible in terms of the admission criteria, where you live and also what the furthest distance away that was admitted was. If it was 0.5 of a mile and you live 3 miles away, then you have little chance of success.
I would recommend that you put down your nearest (or catchement) school no matter how poor you think it is, as this is the school that you have the highest likelyhood of getting offered a place at. If you have other preferences that you prefer put them down as 1st and 2nd preference but under the equal preference system that operates for school admissions putting the nearest school down as 3rd preference will normally still get you a place at that school, if neither of your other two preferences can be offered. That local school is better than a school many miles away that will be offered if none of your preferences can be (that is you have made un-wise choices!)
From sitting on appeal panels for school admissions I would always recommend that you get your form in well before the cut off date if at all possible and that you make sure that you get written confirmation that the LA have received it. Sometimes forms do go astray or you fill it in on line and you think it has gone through when it has not. If the application form is not received then the LA will normally not accept a late application as being on time, no matter what the situation.
The last thing to be aware of is that there will be changes to Admission arrangements that the new government is shortly to consult on. The assumption is that they will not apply to this next year but you never know what might happen. So keep an eye on the school and LA website, just in case.