Most common treatment is time - they get bigger and more prominent over the first 6 months to a year, then naturally start getting paler and shrinking, and a lot are no longer visible by school age.
Most common active treatment is oral propranolol. This has been used for this indication for over a decade (think I first prescribed it 13 or 14 years ago). Generally used for problematic haemangiomas. So those having problems with bleeding or ulceration, or those in critical locations like close to eyes, nasal, on the ear, or genitalia. Personally I also have a low threshold for facial ones, because society is so mean about even temporary facial differences. It usually initially stops the natural worsening, and then usually makes the regression start earlier than it would otherwise. Risks of dropping blood pressure, dropping blood sugar. Because of this we always keep the baby on the ward for a few hours of monitoring after the first test dose. Also needs stopping if they develop wheeze as toddlers, as it stops inhalers working.
More recently a few hospitals (not ours) have started using a topical preparation. Usually seems to be timolol, which comes as a gel to be applied a few times a day. Can't be used if any skin breach. Only seems to work on the smaller flatter milder haemangiomas (basically the ones we wouldn't usually treat at all).
Unless ulcerating, there isn't much evidence that treatment improves the eventual appearance (unless in a location with growing cartilage ie nasal tip or ear), but rather that it reaches the final outcome faster. Personally I suspect that it probably does slightly improve the final appearance, as it doesn't get as bad before it starts improving, hence why I stretch the guidelines to include significant facial ones even if not in a critical location.
Hope that gives you some info.