Help on automatic transmission, tips and tricks from any car experts?

Hello I'm new to driving and was hoping if someone could give me insight. My honda is automatic and has 3 gears. Drive, second, and low. I know low is the highest gear because it increases rpm much faster than drive. My question is, when am I supposed to use something other than drive? Any tricks or hints? When I merge onto the freeway, do I go in second gear, accelerate the. Drop down to drive? Please any tricks will be greatly appreciated

Regular driving,… Just put it in drive ( D ) and forget it it's automatic, it shifts when it needs to

use low or mid gear for extreme hills,… Mud & snow

NORMAL DRIVING, D OR OVER DRIVE. IF YOU ARE ON HILLS WHERE YOU WISH TO CONTROL THE SPEED DOWN HILLS, 2ND. IF YOU HAVE A LOAD, FIRST OR SECOND BUT KEEP THE SPEEDS DOWN.