1) Go through award, page by page, and note each section that has an approval requirement.
2) Note the requirement, the relevant section of the contract, the person who has authority to approve (AOR/COR, AO/CO, etc.), and what form the approval takes (letter, waiver, etc.).
3) Also note that the award may not necessarily explicitly state ‘in order to do XXX, you need approval from YYY.’ In some cases, your award will state a limit (e.g. ‘your budget ceiling is $.5 million dollars’). And you are responsible for knowing that in order to exceed that ceiling, you will need to get approval for a contract or cooperative agreement modification.