Scaling out of positions: best practices?

Hey everyone, been spending a lot of time on backtesting different strategies for $BTC and other alts. One thing I'm still trying to nail down is the best way to scale out of positions, especially when aiming for multiple profit targets. I've tried scaling equal percentages at predefined levels, and also a more dynamic approach where I'd take off more at the first target if momentum seems to be waning. I feel like I'm leaving money on the table sometimes, or cutting winners too short. For those with more experience, how do you typically approach scaling out to maximize returns while still managing risk effectively?