I debated whether to put this under "Mindsets" or "Methods". It's certainly not a method you can pull out of your bag of tricks at a moment's notice, but instead a way to prepare to come up with ideas.
Patterns are common ways to solve an interface design problem. Usually these patterns are common because they have been used in lots of software in the past, so they are "tested" ideas that seem to have few downsides. These patterns have been collected into pattern libraries, often in the form of books or websites. If you have one of these to hand, you can leaf through it for inspiration, and hopefully you find an interface pattern that solves your particular problem, or inspires a solution.
If you don't have a pattern library to hand, pattern knowledge helps as a form of preparation: Look at the ways that designers solve common problems whenever you see an interface, and learn them. When it comes time to solve your own problem, a lot of your initial ideas will be inspired by these patterns you have seen in the past. In this way, knowledge of patterns is a way to come up with lots of ideas quickly.
Magdalene has been asked to design a new screen where the user is shown a list of things and needs to choose a subset of them.
She's seen a pattern to solve this problem in a book by Jennifer Tidwell, "Designing Interfaces". She has a copy on the shelf, so she flips through it and finds the "List Builder" pattern. It shows two lists, side by side, with controls to move items from the original list to the user's created list, and back again if necessary.
Magdalene thinks this will work. She tweaks it a little to take care of some of her specific needs, and walks through it with the developer.