All items and parcels under 500g are a flat rate anywhere in Australia so you just need to use the flat rate option.
Under 250g is $4.20
250g to 500g is $5.40
You can add a bit for any packaging materials you use and a small handling charge, anything between 50c and about $2 is generally acceptable depending on how much time is needed to package things.
You can use 500g red pre paid satchels if you want but they are slightly more expensive.
For items over 500g you have 2 choices. You can use a 3 kilo red satchel which costs $9.60 as long as what you are posting weighs no more then 3k and it fits in the satchel or instead of using the flat rate you can choose calculated postage from the drop down menu and input the weight, dimensions etc and then anyone who looks at your listing will see the correct postage to their postcode.
You should keep all receipts:
- Postcode receipt if you post over the counter,
- Receipt for purchase if you use pre paid satchels especially for any item up to $50 in value as, if a parcel goes missing you can refund the buyer and claim compensation from Aus Post.
If an item is worth more than $50 you should send it by registered post. This costs $2.75 extra over the stamp or satchel cost but includes up to $100 worth of 'free insurance'.
What a lot of people don't realise, is that COD is an Aus Post service and does NOT mean cash on pick up? It is also a most unsafe method for buyers and sellers if you did want cash on delivery.
Unless something is too big or heavy to post then offering pick up is a bit dicey, as if the buyer pays with Paypal you cannot prove delivery. There is nothing to stop the buyer from saying that they never received the item and this then leaves you open to Paypal removing the money paid, back from your account and giving it back to the buyer.