Before I started paying, I first used
http://www.freebmd.org.uk.
This site is especially useful if you know 'areas' where your forebears were from.
And this one, too
http://www.familysearch.org/eng/
The single most important thing, though, is to keep meticulous notes......it'll save you looking up the same things time after time......
Ancestry is possibly the best of the 'subscription sites' and will give you access to all of the censuses from 1841 to 1911.......they often run 14-day free trials where, if you are well-prepared, you can gather oodles of information before you cancel the trial. :o)