Important things to note about collecting data:

• Think about how much personal data you need, and only collect necessary information.
• Make it easy for people to collect, particularly if you have volunteers and inexperienced people on shifts
• Try to get the data into a spredsheet as soon as possible, and have a clear place for that spreadsheet to live, and a clear owner
• You may find some uses for the data that you didn't expect, but try to work out in advance what you need it for. If you want to look at changes over time, make sure to collect time and date information. Usually you'll need weight data if you want to calculate carbon savings. If you are able to separate transactions by user and location, that will help show changes by members and place.