To create a new draft order, click on "Orders" on the left menu of your Shopify admin. On the next page, you can duplicate an existing order or create a new order from scratch.
To duplicate an order, click on the order number of the order that you want to duplicate as a draft. Click on "More Actions" and select "Duplicate".
You can also do the same for draft orders — click on "Drafts" (under "Orders"). Click on the draft order that you want to duplicate and click on the "Duplicate" button.
Note that shipping rates and discounts are not duplicated automatically when you duplicate an order.
If you want to create a new order from scratch, click on "Orders" on the left menu of your Shopify admin and click on the "Create Order" button on the upper right. A new draft order will come up, and from there, you can add details of the transaction starting with the products involved in the order. If the product is not currently listed on your Shopify store, you can click on "Add Custom Item" to add it to your draft order.
You can specify whom the order is for under the "Find or Create a Customer" section. If it's a repeat customer, you can just key in his/her name on the search bar. Otherwise, click on "Create New Customer" to add that customer's information to the draft order (and save it to your Shopify store).
If you want to reserve products to that customer, simply click on the "Reserve Items" option and indicate a timeframe for the reservation.
You can also set a tag for the draft order under the "Tags" section. This just makes it easier to keep track of your transactions.
Other options available on the Draft Order page:
Add discount — if you want to add a discount to the time or the total order.
Taxes — add a tax rate (if it wasn't applied automatically based on the customer profile).
Shipping — add a shipping fee (if it wasn't applied automatically based on the customer profile).
If you're not yet ready to send the draft order to the customer, you can click on the "Save" button on the upper right. You can always come back to it later by going to "drafts" from the Orders menu.
If you're ready, click on email invoice to send the draft order to your customer. You can then mark the order as pending. Once a customer pays for the order, you can click on "Mark as Paid" which means that order has been completed.