I carry-on probably 95% of the time when flying. The biggest challenge is doing it on European budget airlines as they generally have much tighter restrictions. I’m not sure that these tips will allow you to never pay baggage fees (as some airlines charge to carry-on) but they definitely might make your life easier.
One thing I’ve been toying with is getting a Scottevest. I finally saw one in an airport and it was actually pretty nice. They’ve improved since they first came out and I think it would make carrying on that much easier. I have been seeing mixed reviews about their quality though. Wish I could order one from REI so I could take advantage of their lifetime warranty in case it has problems.