Debbie:

Which modules are you using (as this impacts were you turn on Allow Fractional Quantities)? It is a Company Profile option in IC (if used), OE is standalone, and should already be there is Invoices is used standalone.

Order Entry Standalone
Order Entry with Inventory Control
Invoice Standalone
Invoice with Inventory Control

How often to you bill for time versus bill for other things that don't require a fractional quantity?

One of the dangers with turning on fractional quantities is that it's very easy to accidently ship .01 of an item that is only meant to be shipped in whole numbers.