The phrase སེམས་ལ་ལྟ་བ་ plays a central role in meditation instruction. I usually translate this phrase look at the mind. Others translate it observe the mind. I think this translation is not only inaccurate but it leads people to make the wrong effort in their practice.
The relevant word in Tibetan is lta.ba. It means to look, but since it is also used in meditation and philosophical contexts, it is often translated as view. or, in the context of dzogchen the view. (In Tibetan, most verbs can quite happily be used as nouns, a flexibility that makes it easy to be both concise and precise but often presents more than a few challenges for translation.)
In meditation practice, there is a world of difference between look and observe.
The word observe carries the connotation that you are watching and noting what is significant, you are marking or being attentive to something seen. Many teachers teach people to practice this way and many people practice by observing what happens in their minds. From the perspective of mahamudra and dzogchen, this is not meditation. As Jigmé Lingpa writes of people who observe the mind(see page 102 in A Trackless Path):
They track the arising and fading of thinking. With this meditation,
Even if they practice for a hundred years, they spin in confusion.
Rather than observe (thus becoming an observer), look. The point is not to see or observe the mind or what is happening in it, but to look. When you look at mind, you see nothing -- nothing whatsoever. As Rangjung Dorje writes in Aspirations of Mahamudra:
When one looks again and again at the mind which cannot be looked at,
And sees vividly for what it is the meaning of not seeing,
Doubts about the meaning of "is" and "isn't" are resolved.
How do you look at mind? Just ask yourself, "What is mind?" Immediately, you are looking at mind. It's like looking at a mirror. You don't see the mirror. You see reflections, but you don't see the mirror itself. Most people cannot stay in looking at mind for more than a second (and often less than that). That's where stability in attention comes in and all the emphasis on resting and developing stable attention. But all the resting in the world will not lead you out of confusion. That's where clarity comes in, and you spark the clarity by asking "What is mind?"
When you do this, you will probably notice a shift. It's subtle, but there is a more awake quality in your attention. That is where you rest. Realistically, it will fade or crumble. Then you start again: question, look, rest in the shift.
A lot of people make the mistake of sparking the attention again and again, perhaps because they are trying to see something. That approach will wear you out. You will develop a lot tension and, if you persist, you will become brittle and fragile. Not a good path.
When you do learn how to make the shift and rest in the looking, thoughts are not a problem. Thoughts may arise while you are looking, but they come and go on their own, unless you engage them. When you engage them, you immediately fall into thinking, which is, by comparison, a confused state of mind. Sometimes you just fall into dullness, which is also a confused state of mind. When either of these happen, relax and start again.
Over time, you will develop the ability and the capacity to experience stillness, thinking, even powerful emotions such as anger, love, hurt or shame, AND continue to rest in the looking. This is, at least in part, what it means to go beyond thought. To go beyond thought doesn't mean that you don't have any thoughts. It means that when thoughts arise you don't need to engage them, you don't fall into thinking or confusion.
From there, it's not that far to experience the various forms of releasing described in dzogchen and mahamudra instruction. Again, see page 121 in A Trackless Path. For instance, arising release refers to the experience of thoughts arising and disappearing as soon as they arise, like snowflakes landing on a hot stone.
Again, you are not observing the mind here, because there is nothing to observe. To observe thoughts is not that useful because when you do, you, as the watcher, remain enthralled in a sense of self, your identity as the watcher, the observer.
Use the looking to raise the level of attention so that you are no longer engaging experience conceptually. That makes all the difference.