My commute has a big climb that varies from steep an short to long and gradual and a second climb that is short and steep both ways. Before I started commuting, I did the first big climb a couple times to get used to it. Since then I don't do any training, but sometimes treat my commute as training. Some days I will push myself a bit harder on the longer steady climbs or on the short steep climbs. I track my performance with Strava to see my improvement. Over a few months I saw steady overall improvement. Anytime something causes a break in my commuting I feel it again when I get out and build back up. When I actually have time to ride on the weekends, I try to do some longer climbs to work on conditioning, but I don't consider it training for my commuter per-say, just generally trying to improve my fitness.