I've been fighting to get into the cycling-thing for a year now. I have finally found the secret to getting started, and I thought I would share what I found. I only do this because it can be really, really hard to be circumspect about what a newbie goes through when you're even a mildly accomplished rider or you were already in shape when you started.
A little background: I'm not a total potato. I do play Indoor Soccer once a week (as a keeper), but all my sporting life I've played sports that are Anaerobic only (usually as keeper when it applies). You go 100%, then recover, then 100% then recover. The result is that my recovery rate is excellent. I can move furniture with the best of them since I can burst, then recover. But ask me to jog down the driveway and I'll keel over, so from a fitness perspective, I have NO aerobic capacity to speak of. If you're not like me, this may not apply to you, but if you're having trouble getting going, this may help.
First, and most important, if you're like me you NEED TO BUY A HEART RATE MONITOR! Get one with an audible alarm if you're out of your target zone and make sure it has a chest strap (so it monitors continuously. Don't get the one where you have to put your finger on it). I know a lot of people just "listen to what their bodies tell them," but I can't seem to hear my body over my ego. While my ego is screaming "move it, lard butt" my body is saying "Can't.....Breathe....", so after 20 minutes I'm in severe cardio distress and can't go on, so I pack it in. 20 minutes after that I'm ready to go again.
By adding a heart monitor, and heeding the beeping when I'm out of my zone, I instantly DOUBLED the distance (from 5 miles to 10 miles) while only sacrificing around 1-2MPH average speed. And honestly, if I wasn't constrained by a 1 hour lunch, I could probably double it again with a similar sacrifice in speed. My goal was at least 45 minute rides. When the Heart Rate Monitor (HRM) beeps, I slow down, take deep breaths and relax until the beeping stops, then I gradually start to get moving again. Search the web for a calculator for your target zone that includes Resting Heart Rate. Although it seems counter-intuitive, it seems to be more accurate than the age-only formulas. My age-only formula pegged me at 157 as the upper end of my zone, which was impossible for me to maintain. In reality it's more like 162 or 163, which I believe is right because that is right around where I start losing my breath.
Second, although I've heard this disputed many times, for me Higher Cadence = Higher Heart Rate. Lots of guys will expouse on the benefits of a high cadence pushing an easier gear, but these people have descent aerobic systems. So when the beeping starts, I generally drop to a slower cadence. Sometimes I can even move to a taller gear (am I saying that right?) so my cadence goes down but I maintain roughly the same speed, and I see my heart rate back off. Most importantly, do whatever you have to do short of stopping to get back in your zone! Every second you stay out of the zone makes it harder later on to get back in the zone, especially at the newbie level where you'll never be far from the top anyway, so there is no real "recovery" period, so don't wait until the top of the hill or you'll pay later on. Drop to an easier gear, drop the cadence, drop the speed, drop the ego, and drop the heart rate until it stops beeping.
Third, and this one will vary from person to person, but keep track of your rides in some type of spreadsheet. This may mean buying a cycling computer, but they're really cheap and really easy to install (I would get one that includes Cadence. It doesn't add much to the cost). I personally keep things like Time, Distance, Average Speed, Max Speed, Temperature, Heat Index, Average heart rate, max heart rate, and recovery heart rate (a few minutes after I stop). It's nice to see that you're making some progress, and you can usually find the cause when you have a bad day.
What this all equates to, for me, is I no longer dread getting on the bike. I'm actually disappointed when I can't do it on a particular day I had planned. The whole experience is much, much more pleasant without sacrificing the feeling that you've really accomplished something that day to help your fitness, and you're not so wiped out that you drag you butt around for the rest of the day.
I love discussions, so feel free to add to/dispute what I've written here.
JPWKEEPER