Another top-tip which I demonstrated to on my nav test.
When time is up, turn. The examiner asked me whether I could see the disused airfield Raydon(Spelling?, in Essex, I think). I said not or at least that I couldn't recognize it as such but that we would be overhead in 1 minute. As we turned, after the minute was up, he pointed it out to me; it was three different colours of crop which broke up it's layout.
It's one of those tricks of navigation, if you've maintained a heading and a time and checked that it is good, you WILL arrive very close to where you want to be.