You have run one or more half marathons and want to improve your time. Your goal is to finish in 1 hr 45 min or less. For your half training schedule, you need to look at some of those provided by professional runners and coaches, since I have no experience at this level of running. However, following my training running schedule aggressively may well fit your needs, since it can be adjusted as needed.
You have run several half marathons previously and intend to improve your time. Your half training schedule is geared to a finish time of 1 hr 30 min or less. I envy you. Find a coach with the right experience and rely on him or her to supply your training program.
You have run several races at the half marathon distance or longer and want to set a new PR. Your half training schedule will be intense. Your goal is 1 hr 20 min or less. Your coach will have provided you with a program designed to strengthen those features of your running that need it.