There is no one size fits all solution for shipping charges. The way to implement charges varies based on your type of product, availability of information and competition in the market.
The key thing to note is that generally, the more accurately you want to match the actual shipping costs, the more work is involved.
Here are some sample strategies you can use:
Usually just for local customers.
Adding "Free Shipping" to your site can dramatically increase sales. And of course this makes administration much easier.
Note: You need to ensure that your pricing will cover shipping costs.
This is an unders and overs game. Work out your average delivery cost per zone, and charge this.
E.g. Auckland $10, North Island $15, South Island $25
Charge a base rate plus an amount per item. Useful when all products are similar shapes and sizes.
You may decide that all shoes cost $5 per item, while all boots cost $15 per item.
This can vary by region.
This is a charge per total weight. You can setup a table of costs.
E.g. <1kg = $5, <5kg = $10 etc
This can vary by region.
Note that you will need the weights, or at least weight estimates, for all your items.
As above but based on total volume.
It is possible with some new systems to get real time quotes from shipping suppliers. This is not common in NZ yet and does usually require some customisation.