It was not too long ago that I was clueless about riding a bike any longer than about 5 miles. As I mentioned before, I’ve ridden somewhat long distances in the past, but always very slowly and never regularly. Commuting at least 11 miles each way every day successfully requires a bit more knowledge and preparation.
I think the first thing I noticed was that your bottom gets sore pretty fast, and after a while it becomes almost unbearable. I tried buying a new, cushier saddle, but practically the only solution to this is padded cycling shorts (or tights in colder weather). If you’re willing to sacrifice a bit of convenience when changing for some added comfort, I’d highly recommend bib shorts. Maybe it’s just me, but the regular shorts continually need to be adjusted over the course of a long ride, while bib shorts are largely “put it on and forget about it.”
Other cycling apparel, such as gloves and a cycling jersey, are certainly nice but not absolutely necessary. The gloves help a bit with hand numbness, while the cycling jersey’s main advantage is back pockets to make up for the fact that the cycling shorts don’t have pockets.
In terms of gear, the most important other item to buy is a portable hand pump, because you will get a flat at some point. You should also carry a spare tube or some patches and glue, though actually I find that some krazy glue dabbed on to the hole (with no patch) fixes the tube well enough for at least another 100 miles or so. Depending on how tight-fitting your tire is, you may also need tire levers.
Now on to technique. The first difference in technique I noticed while commuting is in the pedaling speed (this is known as cadence, for those who care) between the novices and the pros. The faster and more experienced riders will generally be pedaling pretty fast, at least 70 RPM, even on hills. (To measure your cadence, use your phone timer to measure 20 seconds while you count how many times a given foot reaches the bottom of the pedal stroke. Your cadence is that number multiplied by 3.) All too often when I get to a hill I see a novice rider struggling to push down on the pedals, when all they need to do for a much easier ride is shift down to an easier gear and pedal faster. There’s no shame in needing to get into a “granny gear.” No one but you can tell anyhow, and you will certainly be faster pedaling 70 RPM up the hill on a granny gear than 20 RPM in a higher gear.
While we’re talking about hill climbing, another point of advice is to stay seated if you can. Sure, the pros are constantly out of the saddle on the hills, but the average person is almost certainly less likely to get fatigued and give up while pedaling quickly in a seated position.
Finally, inflate your tires to the maximum recommended pressure. I have 28mm tires and I inflate the front to about 105 PSI and the rear to 115 PSI (front is a bit lower for me for some added comfort). You may be OK with slightly less pressure if you are very light, but not less than 100 PSI for 26-28mm, or 80 PSI for 32-36mm. I’ve seen (and passed) so many slow riders with tire pressure that is so obviously too low. Any tube, even a brand new tube in a brand new tire, leaks air over time. If you haven’t re-inflated your tires for over 2 weeks, I guarantee you that your tire pressure is too low. You may not notice it on short jaunts of 5 miles or less, but it will make a difference of several minutes on journeys of an hour or so.
There’s plenty more I can say on this topic but that’s what I think made the most difference for me. So if you’ve never tried riding 20 or more miles in a day, I encourage you to go out and try it. It’s fun and great exercise!