You can limit the time of your exploration with the Crazy Eights technique. This will help you to keep moving fast in short iterations.

First, you start by selecting one problem and stating the design goals. The problem can be more general, such as defining the steps of a checkout process, or more specific, such as the details of the mechanism to pick the delivery date in the checkout form. Regardless of the abstraction level, it will be one single problem to focus on. Once the problem is defined, you can start the exploration.

Fold a piece of paper in eight parts and try to solve your issue in at least eight different ways. Set a timer to just five minutes; it is okay to add a few extra minutes when you are doing the exercise for the first time. The time limit forces you to keep moving forward without getting lost in the details, sketching one solution after another until the time is over.

Finally, you evaluate the solutions against the design goals. You want to identify the aspects that seem to work well, those that don't, and other areas that you would like to detail further. Based on this, you'll select the most promising solutions to iterate them further in another round of the exercise.

The Crazy Eights technique is aimed at teams, but it is also useful when applied individually. When doing it with more people--normally organized in groups no larger than 10 people to keep the session under 1 hour--you get a higher number of ideas, and you will receive feedback from other people. Even if you sketch on your own, getting external feedback is always very useful.