Have a plan for how you will add rates, and work through it methodically so that you don't miss anything. Understand which rates can be copied to which other rates/periods/accommodation types etc. Understand the big picture before you start working on the rates.
Ensure all the building blocks (Code tables: rate types, rate groups, rate components, rate periods, tax rates and tax groups) have been set up first.
Name all Rate Periods with a year then definition, so that in time, all years are listed together. e.g. 2013 Low Season, 2014 All Year etc.
Putting an amount into a rate is relatively quick what takes time is the rest of the rate set up (component split / rate groups etc). If there are rates with a common set up copy the base set up (where amounts are <none>) to all relevant rates and then add amounts. Essentially create a blank template and add the amounts later.
Have 2 ResRequest screens open when working on rates: Add Rates and Rate Sheet, so that it is easy to switch between the 2. Add rates in "Add Rates", then immediately edit them from "Rate Sheet".
Think about all the possible rates you may wish to book when creating Rate Types bearing in mind what you might need to report on them later.
Consider setting Rack Rates and working with commission for future rates as this drastically reduces the number of rates in your system.
It is better, from a control, consistency and reporting point of view, to set up specific Rate Types, rather than allowing overriding of rates at will. Perhaps have one Rate Type which can be overridden (and on which you can report) and limit overriding on all other Rate Types.