Here are some simple recommendations:
Activity logic: Create a closed loop schedule by having just one project start activity/milestone and one project finish one; all other activities must have at least one predecessor and one successor. Doing so will help the software algorithms to optimize calculation of free and total float and to calculate a realistic critical path.
Milestones: Make sure you have both major and interim level milestones in your project schedule. Doing so will force the system to optimize free and total float based on activity durations.
Constraint dates: in the real world, constraint dates exist (contractual, availabilities, etc...). Make sure these constraint dates are built in, as the system algorithms will optimize free and total float based on them. Constraint dates can also lead to negative total float values for activities, based on your existing activity logic.
Resource loaded schedule: create a what-if version and resource schedule it. The algorithms will look at your resource availabilities and use up available free and total float. If you've also included activity constraint dates, you might find negative total float values for activities that could not be automatically optimized.
Non Resource Loaded Schedule: float optimization will be based on the previously discussed resource availabilities, constraint dates, and closed loop activity logic.
Good luck; You've got all that you need to optimize your project schedule float values.
The one thing I missed was activity calendars. Though most of the work maybe on a 5/8 calendar, there may be some critical path activities you would work over a weekend to meet schedule deadlines.
The other thing to look for is an activity that is split over a weekend, or other non working time. For example, you have a long duration critical activity that finishes on Monday morning at 9 am. Assuming a 5/8 calender, the program is holding out the end date by two days to finish 1 hour of work on a Monday morning. Does that make sense, or would they hang around on Friday to finish it up? Besides, its just an estimate and I would probably trim 1 hour off the duration to correct it.