Open reading is just a term for examining the physical aspects of the card images on the table. Many people read this way instinctively, or their tradition is based in it, but for many readers, especially in English language traditions, it's not all that common.
The simplest way to "open" your reading is to watch for human figures and look at what they're looking at. If the Emperor's gaze is towards another card, then whatever the Emperor is signifying is "looking at" whatever that card signifies. So for this exercise we'll stick with that. In your reading, make sure to include a step that examines all the eyelines of figures in the cards. If you're using a Waite Smith clone, this may become overwhelming. If that happens to you, begin with the trump cards, then move on to any court cards, and if you still feel able to hold all those eyelines in your head, only then move on to the other small cards.
Now, the second part of this exercise is the fun one. We need to focus on eyelines, so we're going to take a spread we're familiar with and mess it up. And we're going to do that by randomizing it.
Here's how I suggest you do this. Take the spread you're most familiar with, and a set of index cards. On each card, write down one card position. So, if I use the Celtic Cross, I would have 10 index cards, each one labeled with something like The Past or Hopes and Fears.
Once you're finished, shuffle these index cards. Lay them out one by one into the shape of the familiar spread. This will randomize the meanings of each position. Now, the typical spatial connections between cards won't be there, while new spatial connections will form. This will also allow you to pay more attention to the eyelines, because you won't fall into the natural habitual meanings of each spatial relationship, since, well, they aren't there any longer.