Jonathan Coulton started by writing one thing a week. Most of them were meh but there were some that were good. Turns out the important thing is perseverance.
once you have a good development for mechanical aspects you absolutely should record yourself and listen, so you can train your ears for the sound. your own ears will lie to you a lot, and the room/hall acoustics matter. the signal gear for amped instruments matters as well. if you want to play for people you have to train your ears so that you know what good sound, sounds like to most people.