While giving instruction about airspace to an airline pilot a while back, he asked me "How on earth do you keep all the different airspace stuff straight in your head?" As a pilot for a part 121 carrier, his flying on the job was always under Instrument Flight Rules (IFR) and that made the finer points of the National Airspace System mostly irrelevant for his day to day flying. I'll be the first to admit that the NAS is very complex. Most non-pilots don't realize that GA pilots flying VFR need to have a much deeper understanding of airspace than most professional pilots flying IFR. Still the answer to his question about how I keep it all straight was easy: "I give flight reviews to about two dozen pilots a year so I'm constantly going over this stuff."
Yet this didn't really answer his underlying question - How does someone remember all these details when you are not an instructor and you're not using this knowledge every week? Many pilots, myself included, cannot afford to rent an aircraft once a week, so I want to separate the concept of currency in flying an aircraft from being able to remember and apply rules, regulations, and procedures. There are several ways to stay current on rules and regulations, but the only universal answer is to read and study a little bit every month.
Most pilots have a subscription to at least one flying magazine and these magazines publish articles on learning to fly, pilot trip reports, new equipment, and accident reports. These articles are a great way to keep the little gray cells active and thinking about the ins and outs of flying. A few of the magazines I recommend are AOPA Pilot, Plane & Pilot, and IFR Refresher. There are others, of course. And remember that just looking at the pretty pictures is not enough - you need to actually read the articles.
Unless you are training for a new certificate or rating, your copy of the Code of Federal Regulations related to aviation and the Aeronautical Information Manual (popularly known as the FAR/AIM) is probably several years out of date. By the way, FAR supposedly stands for Federal Aviation Regulations but, in fact, neither the FAA nor the federal government use this abbreviation to refer to Title 14 of the Code of Federal Regulations. In fact, FAR stands for something completely different. Ah, acronyms!
The FAR/AIM is often described as the kind of book that, once you put it down, you just can't pick it up again. Still, as a certificated pilot you need to stay abreast of changes in regulations and to review the ones that haven't changed but that you might not remember. I recommend that every week you pick a different section of the regulations or another chapter of the AIM and read it. The FAR/AIM is not terribly expensive (less than US$15), but you can also access the regulations and the AIM on line for free.
An excellent on line resource is the publications page at the NASA Aviation Safety Reporting web site. You can subscribe to the Callback newsletter, which contains some very interesting reading, or you can read all the issues in HTML or PDF format.
If you aren't able to fly as often as you like, you can't really learn from your mistakes because you aren't able to make any. So learn from the mistakes of others by visiting the NTSB Accident Synopsis and FAA Preliminary Accident & Incident Reports web sites.
Even pilots who are not AOPA members can access free on-line courses provided by the Air Safety Foundation. These courses provide excellent training, they are free, and they also qualify for the FAA's Pilot Proficiency Program.
Every two years, pilots certificated in the U.S. must undergo a flight review or otherwise satisfy the requirement for a flight review. To be precise, the review must be completed every 24 calendar months. 14 CFR 61.56 gives all the details on the flight review, but the short answer is that you must complete at least one hour of ground instruction (covering the relevant sections of 14 CFR 91) and one hour of flight instruction with an authorized flight instructor, designated examiner, or FAA inspector.
The ground portion must cover the relevant portions of 14 CFR 91 and most pilots have trouble with, you guessed it, airspace. I often find that pilots are not terribly well-prepared for a flight review and so the ground portion takes about one and a half hours to complete. If you want to save some money, study for your flight review!
For the flight portion, I like to ask the pilot what kind of flying they do and where they feel they need work. Most pilots readily admit to the areas where they need polishing and relish the chance to get a workout. Some pilots expect a free ride and I go pretty hard on these folks. If that sounds harsh, remember that the endorsement that the instructor gives you for the flight review begins with the words "I certify ..." Heavy words carry a heavy responsibility.
Another way to meet the requirements of a flight review is to earn a new pilot certificate or add a rating to your pilot certificate. You can also complete a phase of the FAA's Pilot Proficiency Program, commonly referred to as the Wings Program. You attend an authorized safety seminar or complete an authorized training course, then schedule three hours of instruction with an authorized instructor covering one hour of takeoffs and landings, one hour of maneuvers, and one hour of instrument flight.
I think the humane way to do this is to do three one hour flights consisting of 20 minutes on each area. Once you're done, the instructor signs the card you received at the seminar and gives you a logbook endorsement. You send the card in to the FAA and they send you a certificate and a set of lapel pin wings.
On the next cold, cloudy and rainy day, try curling up with with some good aviation material. It will make your next flight review go more smoothly (and cheaply) and it will do a lot more to keep your head in the game than, say, watching re-runs of Survivor.