For me, free will is the feeling and belief that if I want my body to do something I have a pretty good chance of making it do that. Additionally, I can decide to train some reflexive behavior and tailor it to be more of what I want my automatic responses to be. It's a feeling of integration between my desires and my actions that doesn't feel like it's driven from outside my body. For example, if I get a muscle twitch or spasm or a limb falls asleep and I can't move my digits then my sense of free will is lessened. When I walk, talk, etc. then the feeling is reinforced.