Start with zones, not rates
A zone is where you will send things: your own country, a region, the rest of the world, or nowhere at all. Decide that first. A shop that quietly accepts an order it cannot ship is a refund plus an apology, and both cost more than saying no on the page.
Once the zones exist, each gets a rate. Flat is easiest and fine for most shops. If your parcels vary a lot, tiers by cart value keep the small orders from paying for the large ones.
Free over a threshold, chosen deliberately
Free delivery above a number raises the average order, but only if the number is slightly above what people usually spend. Set it at your typical order plus one item. Set it far higher and it is decoration; set it below and you are paying postage on orders you would have got anyway.
Pickup is a product decision
If people can collect, offer it explicitly and price it at zero. Then write where and when. Pickup that exists but is not described turns into a message asking where you are, which is the same work you were avoiding.
Check it as a buyer
Open your own shop from a second account, add something, and look at the total. The cart is priced by the server, so what you see is what will be charged. If the number surprises you, it will surprise them, and they will not write to ask.
One line in the description saves the rest
Say how long delivery takes. Not a promise, a range. Most shipping questions are timing questions wearing a costume, and answering it on the page removes the exchange entirely.