That's not a bad article for someone completely new to the sport. More indepth discussion could be had at all points, but for time/space that wasn't bad. Few things I would add. (as I've posted about mountain bike questions in the 35+forum)
The bike IS the most important thing, and you sure don't want to get a frame that doesn't fit. You can borrow a friends bike to try the sport, but if you are like me, 6' 3'', not many of my friends can fit on my bikes. Any person borrowing a bike that does not fit them properly will have problems enjoying the ride. Check your local bike shop for RENTAL bikes that they can size you up on - then go try the ride. When sizing up for your own bike, make sure you ride it around the parking lot, if not further, before settling on one. All brands are different in their sizing and fitment and how they combine seat tube length to top tube length, etc etc. Just because one bike is cooler than the other, or looks better, cost more, etc doesn't mean it will fit the same/better or even work for your needs. Find a bike FRAME that fits first, everything else can be adjusted and customized. Talk to the bike shop guys about what kind of frame and type of material for the frame you should get depending on the riding you want to do. Steel gives you different ride than aluminum and so on. Full suspension may not be necessary if you are only smooth trail riding. Once you have the bike that fits you the best, the rest is just easy and fun. Remember, there are all types of bikes for different types of riding. Full suspension mountain bike, road hybrid bikes, full on road bikes, beach cruisers, etc. First determine what you want to do, then go look for a bike.
SAFETY FIRST - ALWAYS BUY A TOP RATED HELMET AND HAVE IT FITTED BY A PROFESSIONAL!!! I CANNOT STRESS THIS ENOUGH. (read my post about my wife's accident in the 35+ section) Gloves are good, especially the gel padded ones. If you are prone to hand pain, you may need a thicker padding glove - if not, just plain nubuc or leather will work just fine. Most other equipment is optional as well, except maybe the shorts and a good seat/saddle. Padded cycling shorts, silly as people make them seem, are a necessity if you are going to log serious miles on the bike. Also, in that category, a seat that is comfy. Gel seats, cutaway seats, whatever makes your underside feel good, that's what you get. Some high end bikes come with racing ''saddles'' that are very firm, no padding, and hurt alot if you're not used to them. Jerseys and the rest, buy as you go, if you want. A hydration pack is also a great thing to have. Not only do they hold lots of water, you can usually put a good amount of gear like tools and extra tubes in them, along with MP3 players

. Also , they usually have pockets now for cell phones and ID cards in case of an emergency. A good hydration pack can be had for less that $50 and they make long rides SO much more fun.
On to the pedals. Ah, where to start with the dreaded clipless pedals. Beginners hate them, newbies have scars to prove they don't work, etc etc. I've been through the whole lineup of pedals, and clipless are the best thing ever that you could put on your bike in my opinion. Not only do they give you more control, but once you get used to them, you can actually pedal faster and with more confidence using them. They 'lock' your foot to the pedal with a cleat that is simply released by rotating your heel outward. Most good pedals have adjustments that can be made to them. Start out by setting this as low resistence as it will go. Practice clipping in and out of your pedals with both feet while supporting yourself on a wall, or someone holding you up. Once you are confident with them, start pedaling on the road. Notice how they feel, and how you can PULL your pedals up as well as push down on them. That is the advantage of the clip-in pedal system. Pulling your pedals back up = hamstring workout from HELL!! Also, when going over rough terrain, your feet will stay on the pedal a lot easier than with regular pedals or even the cage/toe clip style. If you get these pedals with your bike, they usually have an insert that makes them look like regular platform style pedals on one side, and the clip in style on the other. After you get your bike dialed in, seat and brakes just so, and all the little things perfect, give the pedals a try you'll be glad you did. There's a reason the pros all use clipless pedals - it's safer and more efficient.
BTW- shoes, find whatever feels good and go with that. If you have the clipless pedals, then you will need a shoe that can accept the 'cleat' - this will be noted on the shoe. Just make sure you buy the shoe that goes with your pedal, ie if you have shimano pedals, you will need a Shimano SPD compatible shoe.
Training/riding - now the fun begins. If you are just out to get some good cardio workout and mainly riding roads, you might want to buy a trip computer for the bike. This will tell you a bunch of different things, miles ridden, time, ave mph, and so on. Good for benchmarking and racing against yourself. When on the road, try to keep your cadence, or pedal pace, consistent and add bursts of speed every once in a while. This will give you an amazing workout and help you chanage up the routine. Imagine yourself pedaling and moving your feet in perfect circles with equal force on up stroke and down stroke. This exercise will help develop smoother pedaling and more efficient riding. The workout this gives on your quads/hams/calves and every other muscles in your leg will be felt for DAYS after the first few rides, just keep at it. Keep your butt as motionless in the saddle as possible. Chug those legs, don't rock back and forth to generate power. Imagine your legs like two pistons, up and down, forward and backward. There's your power, not from rocking your butt in the seat - that'll only give you saddle sores
If you are riding trails, and want to ride technically challenging stuff - there are some things you should practice. Stop stands - practice balancing while NOT pedaling. This comes in handy while waiting at stop sign/traffic lights , or waiting for a friend to cross a log on the trail. Practice bunny hopping. This is the most versatile trick - hopping rocks and logs on the trail will be made easy with clip in pedals and plenty of trial and error. Practice braking with one finger, both front brake only and rear brake only without skidding or flipping. Learn how to shift your weight front to back in order to avoid going over the handlebars in a front brake maneuver. There might be a time when your rear brakes don't work, better to know now, than learn the hardway later. Realize when climbing a hill, you want butt and weight over the back tire and low center of gravity for better traction. Always look ahead of you, and past curves - try to pick a line in the curve that allows you the smoothest transition and least amount of ''steering'' MOST IMPORTANT: do NOT look at anything (rock, tree, drop off of trail) that you do not want to go towards. THis is a subconscious thing that has been proven true by yours truly. If you don't want to go there, don't look there. If you want to look - stop and look. Another beginner error - shifting with full chain tension. In other words, shifting AFTER the hill begins and you can hear the chain go CLUNK...CLUNK..and they try to shift for an easier gear, but it's already too late. Shift early, with little tension on the chain - it will make your riding easier and you chain/cog set last longer. You also won't have to worry about chain suck or deraililng your chain, spinning your pedals really fast, and then crashing to the ground after bouncing your private parts on the top tube...not good. Start on easy trails and work your way up. Time in the saddle = experience on what to do. Sure you're gonna crash. It happens to everyone. I've crashed lots of times - makes for good stories over a beer later that night. If you have on your protective gear, and can ''crash smart'' you should be ok. By crash smart, I mean: know your limits - if something is too difficult, walk it. If you are going to crash, try to get your feet free from the clip in pedal and get ready to tuck and roll. Don't try to catch yourself or your bike. YOU WILL GET HURT DOING THAT.
Biking is a great deal of fun, and an awesome workout as a bonus. When my wife and I were dating she said that her and her friends noticed my ripped up legs, and thought they were the sexiest things around. I never really noticed, but since then people have confirmed. ''dude your legs were huge back then - how did you work them out?'' I was 6'3'' about 190lbs, all in legs. I didn't. I only cycled. All the time, road, trail, whatever. It's like anything else - an addiction. Once you get in, there's no getting out. It's great. You'll get huge legs, great cardio, and you get to look like Lance with those cool spandex shorts - what more could you want?!?!