Assume you have to actively pursue. Some areas put posters up in nurseries etc, but it's down to you to find out which primaries you might get into ( look up their admissions policies on their websites and that of your local LEA) and register your preferences, often online. It's your responsibility to read the admissions regulations and understand your options. Ask on here too, lots of admissions experts as well as those who have been through it!
If your child is registered for the 15 hours free nursery, you'll usually get a letter from your council letting you know it's time to apply. Different councils open their websites for applications at different times of this term; ours is mid-November and the letters only came out a week or so before last year. The next local authority to us geographically opened their website last week. Either way, all have the same closing deadline of mud-Jan.
I only know about the London system, but we looked at all the schools within a mile radius online, took out the faith ones as we're complete heathens and didn't have a hope and then looked at the 'last distance offered' on the council website.
I then went to visit 5 of them and read the Ofsted reports and interrogated anyone on the local bus with a child in uniform!
Visiting is the most useful - 4 of the 5 I looked at were Outstanding but they were not all equal. I actually listed a 'Needs Improvement' before 2 of the Outstanding ones.
Use all of your options:
1st choice - your absolute favourite even if you don't have a hope (we eventually got ours via the waiting list) 2nd - 5th choice - others in order of preference 6th choice - a dead cert even if you hate it. Better a school you hate at the bottom of the road than a school you hate that requires 45 minutes and 2 changes of bus to get to.
Waiting lists can and do move, so don't panic if you don't get your first choice.
In our area I think you just have to pursue it yourself. Dd will be starting in 2017, I haven't been contacted by anyone but I have phoned the schools myself and most of them have open days in October or November, which ive booked onto (no idea if these fill up).
There are four schools which dd should be able to get into so I'm going to see them all. I have some idea which ones I prefer (not the church school or the one which failed it's Ofsted), but I think the visit will be the most important thing. If anyone has any suggestions for questions to ask or things to look out for, that would be very helpful!