While I'm on the course, if I'm not on the tee or close to the green, I seek yard markers or stakes and estimate (by roughly stepping off or eyeing-out) how many yards I have for a given shot. For what it's worth, I have been pleased with my play.
What are the benefits of rangefinders? How would a rangefinder make me a better golfer (not from a results perspective, though it would go hand-in-hand, but from a perspective of refining my skills/game)?
Rangefinders can be a valuable tool but to get the greatest benefit it is important to do some homework before setting onto the course.
A rangefinder provides accurate distances to objects on the golf course but unless you know how far you hit each club then there is little benefit in having the greater accuracy. To get the most use out of a rangefinder it is advisable to accurately measure the average distance you hit a golf ball with each club in your bag, either by using the rangefinder on the practise ground (hit a number of shots with the same club and get the average distance of all the good shots) or if you don't have practise facilities that would allow measuring (like a public driving range) then measure the distance of your shots during each round of golf you play to build up the data.
With this data in hand a rangefinder provides a lot of benefits during a round:
Speed up play: By removing the need to accurately pace out distances from yard markers, plus club selection requires less thought.
Confidence: By removing doubt about distance and which club to choose you may feel more confident in your shot. The fewer uncertainties going through your head when taking a shot the better, and being able to know your average performance with a club you can feel confidant that you can reproduce it.
Decision Making: By using a rangefinder to measure the distance to different hazards on the course you can improve your decision making ability. If you can measure the distance needed to clear a fairway bunker you can plan accordingly whether it is worth the risk to attempt, similarly knowing distances can give you confidence in laying up closer to a hazard than you would normally do
Motivation If you keep a track of your average distance for each club with a rangefinder you can track the small improvements you make in your game over time which you may not notice from purely looking at your final score.
Calculate the effects of slopes and hills This is really only a feature of more advanced rangefinders, but some have the function to calculate the elevation of where you are aiming and automatically take this into account and give you a comparative distance to the target.
Data Gathering A rangefinder is the most convenient tool for gathering distance information on how far you hit each club. Just knowing this information gives you an advantage over many other players you'll play against.
The caveat to all this is that if you wish to actually compete in tournaments many clubs forbid the use of rangefinders, or if they are allowed they often must be the type that only give information about distances (some more advnaced one can calculate distance taking into account the slope of the course and possible changes to distance due to atmospheric conditions!)
Basically, a rangefinder's advantage is that it tells you exactly how close you are to the pin (or to some other object you're rangefinding), instead of approximately how close you are based on your relative distance to some other known marker, like the approach stake. With a good rangefinder, it's possible to get an accurate distance reading (usually within a yard, sometimes to tenths of a yard) on almost any object on the course, from the near to far edge of a dogleg landing, to the rocks at the near edge of a water hazard, to any stake, tree or other significant landmark through the green, and of course the pin.
In the interest of full disclosure, any device intended to be used for distance gauging, or any device incorporating this ability as a major feature of its design, is disallowed by strict rules (Rule 14-3) under penalty of disqualification. The Rules, however, also allow courses to implement a Local Rule allowing them overriding 14-3, and for casual play, virtually all courses do allow them, with many even providing such a device in the form of GPS systems in the carts.
Rangefinders have the most benefit on courses where planning your shots require you to know more than just the distance to the pin, and on courses that have more limited information along the way. If you need to know how far it is to that dogleg landing, so you can drop your tee shot there before changing direction, and there's nothing useful on the scorecard map or in your cart to help you gauge it, then a rangefinder will definitely save you a few strokes finding out by trial and error. Similarly, if the holes only have yard markings from the tees and no other distance aids through the green, and you can't rely on "dead reckoning" based on the average distances of your clubs (due to high winds, or the fact you're hitting shorter or longer than you'd expect on that day), a rangefinder can be invaluable.
On many courses I've played, however, you usually have at least an approach stake telling you you're, say, 150 yards from the edge of the green, and given where your ball actually lies relative to that stake, and how far back the pin is from the edge of the green, your distance to pin can be reckoned accurately enough to drop your ball on the green within putting distance from there. Most obstacles, similarly, are positioned such that playing over and around them is relatively natural; you can, at the very least, play it safe your first time on that course and hit away from or a little softer than you normally would, and then when you're sure your next shot will carry the hazard, you hit out longer. Your next time out, knowing how you played it last time, you might go for more club and a stronger swing to carry the tee shot over the hazard, setting up an easier GIR or even a birdie try.
