I often get out on foot for a nose about any likely looking areas, the beauty of this is that you can combine it with a nice walk with your wife ("Is that your folding saw in your pocket, or are you just pleased to see me ?" - "Of course it's my saw love, we're going for a walk aren't we ?").
An odd time Google Earth can be useful, but around here the tree cover usually means that you can't see a lot.
In forestry and on open moorland I just ride anywhere - unclassified roads, footpaths, sheep tracks - plus I have obtained permissive access to a few tracks around here that lead through farmland and up onto the open moors (intack roads).
We don't have much trouble with access here anyway, so most people's routes end up including a fair amount of "cheekiness" - the secret with cheeky trails is to keep them known only to people who appreciate them and understand their status (or lack of it). A few have been blown by being mentioned on forums etc. meaning that next Sunday you have a group of 20 trampling all over the place......
Local knowledge is the answer, get out and explore and nose around, look at old maps, talk to the people (farmers usually) who really know the area - or move to Wales or Scotland, where you'll have more places to ride than you can shake a stick at - I actually think that I'm extremely lucky to live where I do too, there's masses of good riding which I probably tend to take for granted more than I should.