In addition to the above, I track:
- ride time
- total time
- total climbing (accumulated elevation gain)
- average & max HR as recorded by my HRM
I generally try to compare apples to apples, e.g. no fair comparing 25 flat miles to 25 miles with 3000' of climbing. I don't get too hung up on evaluating performance; at best what I'll do is look at a route and then look at my previous efforts on that same route and compare times, speeds, HR stats to get some sense of how I'm doing.
No; many times that's estimated. I am not so anal that I need it down to the exact foot; "pretty close" is sufficient for me. I use a program called KLIMB that has elevation info for our local area (and some others) and I typically use that.
There are some HRMs/computers that have altimeter functions, but I could not justify shelling out that kind of $$$.
Yeah, theoretically you can add your own info to KLIMB, but it would take quite a bit of time and effort. For your situation you might be better off getting a GPS or something like that. It's possible Google Earth's info is good enough. Though I suspect there is decent documentation of climbs/routes in your area, you should maybe ask other cyclists around there how they keep track of elevation.
It's definitely a good data point to add unless all of your routes are really flat or nearly so. Changes in my climbing ability are, to me, the best indicator of my progress and fitness -- much more so than distances, speeds, etc.