If you are doing a Gap Assessment I would start at the top of the standard and march right through it clause by clause. Use the EMS manual as a reference and make sure all elements of the standard have been addressed.
If you are planning an internal audit I would consider using a process approach where you audit many of the clauses almost simultaneously in each department or functional area of the organization. The following is an example of a line of questioning you might consider when you are interviewing employees in a Maintenance Department (MD).
Auditor: What are some important environmental aspects of the maintenance department?
MD: We clean and paint equipment used in the mine so we generate solvent waste and we have air emissions from the spray paint operations.
Comment: If the aspects match those on the record required by 4.3.1 you have some evidence of conformance to 4.3.1 and 4.4.2. If you see parts cleaning operations and painting operations being performed but these have not been identified as environmental aspects you may have nonconformity to 4.3.1. If these aspects have been identified but the MD representative you interview has no idea about what an aspect is or any of the impacts from parts cleaning or painting you may have nonconformity to 4.4.2.
Auditor: How do you make sure that waste solvents are handled properly?
MD: There are some important laws we must comply with for these waste solvents and we follow our Waste Solvent work instruction.
Comment: You now have some evidence that they have identified the legal requirements 4.3.2 and have established operational controls of significant aspects 4.4.6.
Auditor: This section of the Waste Solvent work instruction says the waste solvent storage area will be inspected weekly and the results recorded on the inspection sheet. Can you show me a record of the inspection that was performed 2 weeks ago?
MD: Sure here it is.
Comment: With this question you are looking for evidence of Operational Control 4.4.6, Monitoring and Measurement 4.5.1, Internal Audit 4.5.5 and Record 4.5.4. You could even get Corrective Action 4.5.3 if problems are found during the inspections which were corrected.
Auditor: Can you tell me about what you do if you see a fire somewhere in the facility
MD: We have been trained in proper use of fire extinguishes so if I think I can put the fire out I will try. No matter what, I will call the designated emergency coordinator who will follow-up and I will evacuate to my designated assembly area in the parking lot across the street.
Comment: Here is evidence of 4.4.7 and 4.4.2 and maybe 4.4.3.
The potential audit trails you can follow in a department are almost endless and each trail should be able to give you evidence for one or more clauses of the standard.