For normal driving, let the engine rev more smoothly. Don't put so much throttle input in. Smoother feet = smoother shifts. What you're probably doing is getting into boost in first gear and then shifting before the car has time to settle (it still want to accelerate, and then all of a sudden you're pushing the clutch in and putting it back to an idle). Just be more careful with your right foot and accelerate slower in normal driving.
If you want to take off from a light semi-fast, just let the engine rev more. If you're giving it quarter or third throttle, let it rev all the way to 3500-4000.
This stuff is hard to explain, but easy to do. Just try different things. Driving a manual smoothly is all about balance and learning to communicate with the engine and letting the engine talk back to you.