Previously, the player could use any of his clubs to measure out a club-length.
Now, a club-length is defined as the longest club in your bag, except for the putter.
Good to know: Using extra-long, “broom handle” putters for measuring is thus no longer allowed.
Dropping (Rule 14)
Previously, the ball had to be dropped from shoulder height.
Now, you have to drop from knee height.
Good to know: If you drop from shoulder height out of habit don’t worry, just pick the ball up and drop it again correctly, without penalty.
Distance measuring devices (Rule 4)
Previously, they were only allowed if they were expressly permitted in a Local Rule.
Now, you are always allowed to use distance measuring devices unless this is prohibited by a Local Rule.
Good to know: In practice, this rule changes virtually nothing as almost all golf clubs already allowed distance measuring devices.