If no one sees you, then you won't get busted
We have a few rules of our own. We don't hop fences or deliberately ignore 'no trespassing' signs or anything else that might indicate someone wouldn't be too pleased to find us there. We tuck ourselves away when no one is looking.
Here's more we've written on wild or free camping
A lot depends on where you're cycling. In Germany, for instance, you have to be fairly discreet because landowners are more protective and likely to call the police and although you probably won't be fined, being told to move on near dark or after dark isn't great. In the Middle East, we were repeatedly 'found' by shepherds but no one ever minded and more times than not, they insisted we come home with them or asked if we had enough blankets or brought us sugar and bread. Sweet people.