A lot of new creators struggle with how to plan and create their rewards (and add-ons) for Kickstarter projects. Here's my step by step process:
1. Plan Rewards & Pricing Feedback
First plan the item or items you want to create generally and figure out how much it will cost to make. Your base cost is any printing/production costs, shipping to you, and also your time to create and fulfill this item. For example if you are planning to make a book you'll want to price it with your printer/publisher for the size, length, and quality of printing.
You'll also want to consider your time to make the content of your book and if there's any time needed for signing it or doing any special packaging. Not sure about prices? This is where you can present several options to your fanbase and get their feedback, remember even with Kickstarter's cut it should be a better deal there than retail pricing later. One way to make it a better deal is to include low cost extra items like stickers and bookmarks at no markup, or even include digital rewards for free with your physical ones.
2. Check the weight and shipping costs
Once you have a plan of what you are making you'll want to work out the weight and shipping costs. This can be a bit tricky. To save time I recommend breaking it down as follows:
First figure out the weight of each item that will be available separately. So if you are, for example, offering a book in a reward set but ALSO as an add-on item by itself figure out the weight for JUST that item.
Then figure out the weight for combined sets of items you'll be offering in reward tiers.
Remember to figure in some weight for the box or package you are shipping in and figure out what shipping supplies you'll need for each set.
This can be approximated for some things as add-ons are generally combined into sets folks are already getting so you'll need to allow for a little variation in packaging and package weight.
Now check the pricing for shipping based on your weights. Keep in mind shipping CAN change overtime. I generally avoid shipping during the holidays due to delays and rate increases. I also expect USPS to have some rate adjustments in January every year. I've found that this usually means some packages cost 50 cents more and others 50 cents less so I just allow a little extra in my budget just in case.
I HIGHLY recommend using Pirate Ship for shipping with Simple Export Rate for International shipping. This usually leads me to price my shipping as US, Canada, all other International.
2. Create the ITEMS first
On your Kickstarter begin by creating an "item" for each reward item. Items are simply a name and optionally an image (you can always add the images later on too).
3. Then Create Reward Tiers
Create the reward tiers you'll be offering. Generally you want no more than 8 to 10 tiers as it's too overwhelming otherwise and backers can customize with add-ons. You can create a tier and copy it to edit to making setup easier for similar tiers. Each tier should have an image of what it includes, but limit your descriptions to short or not at all, as there's also lists of all the items included.
4. Then Create Add-ons
Next create add-on rewards for any of your items or sets of items folks can add on to your rewards. You'll want to cover shipping for these items, but can expect to combine SOME shipping so you can generally subtract most whatever your cheapest reward shipping is. For example if your lowest reward tier has $5 of US shipping and $10 of international shipping you can probably subtract $4 US and $8 INT from add on shipping for any items that can be combined WITH those rewards. If you have large add-ons that have to be shipped separately you'll need to include full shipping.
5. Pick a good pledge manager...
If you are not using the built in Kickstarter surveys (only really works for very simple projects without any add-ons later) you'll want to pick a pledge manager for surveys etc. At this time I recommend Pledge Box and am mentioning it here because they will import all the items and rewards you spent time setting up on Kickstarter which saves a LOT of time later.
Hope this info helps!