I have been auditing packaging vendors in Australia and New Zealand for a number of years and understand how hard it can be getting started.
Have a look at the BRC web site and lookup the Packaging Audit guide. This will cost you some money to purchase but is a really good programme.
Be careful when auditing packaging vendors in that you need to understand how their packaging conversion process works, to ensure you capture all the key aspects of each manufacturing site.
We conduct pre-audit reviews for packaging vendors too and its amazing how many gaps you find in their systems. We are working towards BRC auditor certification in the future.
Be careful of any local government requirements for waste and air pollution. Solvents venting to the air etc.
Primary packaging vendors should all have a HACCP programme.
The IFSQN have really good Quality Systems that you can purchase on this web site, see the Store button above. These show what the packaging vendor should have in place for BRC standards/Certification. Well worth the investment, as it will save you a lot of time and cost.
We can offer you a packaging specialist service if you have a budget to spend. Our web site is www.prd.net.nz