In the months leading up to my participation in the BHF London to Brighton my brother-in-law and I went out on several "training" rides to get some distance under our tyres and prep ourselves for the 54 mile journey.
Towards the end of the "training" I started to venture more and more off-road, and on one particular ride found myself on the trails that I used to use back when I'd go out regularly because the fields and tracks were literally on my doorstep: http://maps.google.co.uk/?ll=51.923732,-0.39156&spn=0.058332,0.169086&t=h&z=13
It took me back, and I realised how much I missed it - travelling down tracks without the worry and grief associated with riding on tarmac.
I was spoilt back then as it was there for the riding without having to look very far at all. However, now where we live is more rural, but the tracks don't seem as abundant.
I've found a few, but purely by venturing down a bridle path and seeing where it takes me (sometimes to dead ends).
What's the best way of finding them, do you know any round near me (J12 of the M1), or is the best way to simply stumble upon them ad-hoc?