I started 7 years ago, not only commuting but completely car-free. I didn't know that bicycle commuters (other than college students and people going a few blocks) existed in the USA. So I started with zero knowledge and no cycling experience, determined to just do it, making it up as I went along. It was only 2-3 miles back then.
The biggest differences that come to mind, then and now, is that a distances are so much shorter now, and the hills not nearly so steep. And a little weather is not so much a challenge. I don't mean to sound smug but it's true, and to me, it's a little amazing.
After a couple of years I got a real job and 11 miles each way. I thought I had it pretty much down by then and most days I'd been riding that distance or more anyway, at least in the summer, so I figured it was doable. I still didn't know any other cyclists let alone commuters, or about this forum, so I was still winging it. I expected a challenge though, and I confess that I bought a car for backup because I wasn't sure I could handle it. I wasn't about to screw up this job by not being up to a bike ride on a bad day. As it turns out I needn't have worried - since then I've logged 18,000 miles commuting and 93% of my commutes to work by bike. Lately, 100% by bike.
Up until then I was riding strictly in street clothes, like most inexperienced riders. Bundled up, rain jacket, anything to keep the weather off. That clearly didn't fly on a longer daily commute, particularly to a more upscale, image conscious professional office. So that's another thing that has changed. My attire, and attitude about attire, evolved from "regular" clothes to more cycling specific. Athletic wear, shorts, jerseys. And a lot less of it, on a given day.
The old bike I'd been riding gave out some time before then, beat up by a right hook while laden with groceries, but it was on its last legs anyway. Barely maintained, just enough to stay rolling, again typical of the newbie commuter. Even the dry-rotting tire was lashed up in ways better left buried. I don't do any of that any more, another big change in my commute. For a few hundred miles I rode my wife's MTB, a too-small big box bike we'd picked up earlier. It was horrible, and I don't do that any more either, another evolution in my commuting. During that time I spent weeks in practically total immersion research of everything about bicycles - much of it the same subjects and arguments that we see in these threads - and picked up the cheapest bike with acceptably reliable frame, components and performance. That served me well and I'd do it again.
A couple of years into this job and several with the cheap bike, I had another evolution of my commute, this time equipment. I built a more traditional road bike, with all standard and more or less modern parts. By then I was capable of literally all of the maintenance and repairs necessary - for that particular bike - and I'd often reconfigure it for different purposes, my version of the n+1 bike collection. But mainly it remains a standard road "racing" bike (with no excessive concern for weight) and that's how I roll now. From 30 year old touring bike carrying a tool box and huffing up hills to travelling light and fast on a road bike. And I have a backup bike, vowing never again on a department store MTB.