Your warm ups should include lay-ups, passing skills, concentration drills, shooting, defensive footwork and rebounding. A small amount of time should be allotted to scrimmage and execution of patterns or defenses. I do think it is your job as a coach however to be alert to your teams warm-up habits and intensity. Too often coaches stand and visit with their counter parts and the players warm-up can drift between two much intensity and sleep city. If you have an assistant they can assist you in this job as well.
Half time is a little different animal.
Half time should be used to make adjustments. If you team is getting beat by a certain scheme on offense or defense and you don't give your team clear alternatives how to overcome the problems it is much more difficult for them to charge out on the court motivated with doubt in their minds. Half-time talks generally should be informational. Keep the screaming and yelling to a minimum because you want them to be able to respond if and when you must chew a few ears. There are times you must get after them though.