For your book:
1.Name
2.License number
3. Suburb
4. If unsure species and number code
5. Any movement numbers import/export numbers...
For you and your snake:
1. Feeding Details
2. Shedding Details
3. Weight/length Details if available
Each individual will keep records to a different standard, some only record basics ie, date, stage of rat/mouse fed (Pinkie, velevet, weiner), and date of slough, others will keep more complex records, ie date, size of rat/mouse (in grams), date of slough and any difficulties encountered, weight, length and any other information that is pertanent to that animal (vet visits, medication, cooling & breeding if old enough, and other observations if needed). I guess it comes down to personal preferance how much you want to know about the snake you are buying.