As soon as you are in the park and purchase Maxpass (which takes seconds), you book one FP. Then you keep booking them every time you’re eligible to pull a new one. When that is is explained here:
https://www.disboards.com/threads/the-answer-to-when-can-i-pull-my-next-fp.3634984/#post-58222160
My personal strategy is to do several rides with fast return times first thing in the morning (things like Big Thunder, Buzz Lightyear, Star Tours, Matterhorn) and then pull something for farther away, which is going to give me a 90-minute “wait” (like Space Mountain, or if you’re parkhopping, RSR or GOTG). By late afternoon, the only stuff left is often the less popular FP rides like Small World, Haunted Mansion, Goofy’s Sky School, so we pick those up then.