The private pilot's certificate is a magic door that opens to the fantastic world of flight. And for many pilots, the sheer pleasure of recreational flying is sufficient. But others soon bridle at the limitations of VFR-only operations when they realize many flights have to be cancelled or delayed because of weather. Often that weather is relatively benign but sufficiently adverse to preclude prudent pilots from venturing aloft under visual flight rules. The instrument rating increases the utility of even the most basically equipped airplanes and eliminates many-although not all-cancellations and delays. Unless you're lucky enough not to be a slave to a schedule, and if you have no intentions of using a general aviation airplane for relatively reliable transportation, then the instrument rating isn't a necessary add-on rating. On the other hand, if you do want to use an airplane for going places, the instrument rating really is a prerequisite.
Learning to fly by reference to the instruments requires three different skills-control of the airplane, the ability to navigate from waypoint to waypoint to the destination, and the competence to communicate effectively. Controlling the airplane under instrument conditions means flying with precision; navigating requires you to know where you are, where you're going and when you're going to get there; and communicating effectively means learning to understand what you're told and being able to express yourself succinctly.
When you first start instrument training you'll be overwhelmed trying to juggle the three skills (aviate, navigate and communicate) but eventually, with practice, it'll all come together.
Controlling the airplane with reference to the instruments requires two things. You have to develop a scan that will let you constantly survey the instruments-concentrating on those that are most useful during the particular phase of flight-and you have to learn to believe what the instruments are telling you.
If you've never seen or been the subject of a spatial disorientation demonstration you may find it difficult to understand how misleading your senses can be. Your instructor will stress that you have to believe what the instruments are telling you and ignore any contrary information from your body. A spatial disorientation demonstration is very persuasive.
Initially, you'll work to refine the instrument skills you had to demonstrate for your private certificate. You'll soon learn which instruments are giving you the information you need during various maneuvers. Don't ignore the value of a desktop simulator or procedures trainer for developing your scan. You'll also learn that there are specific power and pitch (attitude) combinations that always result in the same performance. There will be combinations you'll use for holding patterns, for descent with the gear and flaps extended, and for climbs. In instrument conditions, trim is your friend. Use it. If the airplane is equipped with an autopilot you'll be expected to know how it works and the ways to eliminate it when it's not helping. Be sure your instructor is willing to let you use it. For single-pilot IFR operations in serious instrument conditions, a functioning autopilot is almost a go/no-go item. Once you're comfortable controlling the airplane with reference to the instruments, you'll begin flying approaches. Flying approaches is simply a matter of tightening the tolerances for the four basic maneuvers you've been practicing: straight and level, turns, descents and climbs (for missed approaches). As you fly approaches your navigation skills will improve because of the reduced margins for error allowed during approaches. The instrument ground training should have taught you how to "brief" an approach and how to mine the critical information from the chart that you'll need to fly the approach safely.
When you're first learning, a useful exercise is to either ride in the back while another student flies approaches, or fly them yourself without the view-limiting device so you can see exactly where the approach takes you over the ground. You'll be surprised at the effect that even small control inputs have on your trip along the localizer or down the glideslope. It's one way to see the effect of "chasing the needles" on the approach path. The rule is that if you get a full-scale deflection on either the localizer or the glideslope, you should execute a missed approach and go around. If it becomes obvious sooner that things aren't working out, don't force the issue; plan to arrest your descent and fly the missed approach procedure. But remember the go-around procedure is based on you beginning it from the missed approach point and not before.