What are Operations Specifications (OpSpecs)?
Putting aside the legal definition for someone else, they are a set of rules that an operator (an airline for example) agrees to operate by. The FAA has to approve them. The ops specs can be more restrictive than applicable FAA regulations, but never less restrictive (as I remember). They cover many things, some of which (that I can remember) are:


Type of equipment you're going to operate.
Where you're going to operate.
Extent to which VFR operations will be allowed.
Types of navigation equipment permitted.
Who you can offer your services to.
Crew training required.
Duty and flight time limitations.
Disciplinary protocols to follow.
Flight planning, dispatch, flight following requirements.
Lists of who is who: chief pilot, flight standards director, etc.


There are a lot more areas, but basically it's how you're going to operate your airline. The thing to remember is to give yourself as much leeway as possible. Don't do something stupid like saying that if someone fails an alcohol or drug test that you're simply doing to fire them. Provide for as much VFR operation as you can possibly get the FAA to agree to. Don't saddle yourself with impossible maintenance requirements if you have a mechanical problem in, say, Harare.

Ops specs are best written by someone who has been around the block many times. Write them poorly and you're going to cost yourself a lot of money that you would otherwise not have to spend. If you get a recalcitrant FAA inspector, it's worth fighting it out. Appeal as necessary until you get what you need. Don't be afraid to show up the ignorance of FAA newbies that may have been assigned. Also, remember that the FAA regions are not standardized. It may even be worth considering changing the region where you're technically based to get what you want.