Signal early, nudge yourself over into an open space without actually committing yourself to signal your intent.
Correctly adjust, and trust your mirrors. I have my wife look down to the blind spot below where she sits, which seems to be the only real blind spot. I glance at the side cameras, but they don't show much that is useful.
I tend to drive in the right lane on a 2 lane highway, and in the middle lane on a 3 lane highway. Follow the commercial truck drivers, and let them blaze the trail. They will often signal you when it is OK to move over, and I will also do that for them. When I pass a vehicle, I carefully monitor my mirrors to confirm that the space is still available when I need to move over.