Checkride readiness
One way to tell if you're getting close to signoff is if your instructor says little or anything to you after he/she asks you to execute maneuvers. If your instructor is still barking at you to hold heading, watch airspeed, altitude, step on the ball, etc., you are not ready.
A good, conscientious instructor will demand virtual perfection. He/she will keep honing you on maneuvers that are barely within standards. I did that (1) because it sets up the precise flying habits and thought processes you'll need to fly advanced aircraft down the road and (2) as a hedge against nervousness during the flight test, to ensure that on that day your performance meets standards. Also, a good instructor will hammer you on the oral and ensure you are prepared. Well-prepared Private applicants usually find that the examiner was not nearly as tough on them as their instructors.
I still remember my Private ride, in Chickasha, Oklahoma, nearly twenty years ago. My instructor knew all the gouge, so I knew what to expect. The examiner only looked briefly at MCA, one stall, and one ground reference maneuver. My soft-field landing was horrendous. In any event, the oral lasted maybe .7 and the flight .9 (he wrote down 1.0 in my logbook). It was much, much easier than I expected.