Step 1: Identify the parts of the cup
My examples use a Tim Hortons cup (for some reason they have dropped the apostrophe...), but I have used this technique on many other brands of coffee cup. The pull-up tab is that thing in the lid that you normally pull up, bend back and then snap onto a little ridge in the middle of the lid. You can see how it is normally used the third photo.
We're going to use this tab to create a spill baffle so that bumps on the road (or walking, etc) are less likely to cause a spill.