Which are the best meditation practices to prevent enhancing one's sense of self?
Any meditation can do this, since meditation develops non-attachment and concentration on non-self centered objects, and it's attachment and self-centered thoughts that give rise to and perpetuate the sense of self. Therefore what you do depends on your disposition, challenges, pre-existing beliefs, etc...
However, if you need some pointers, here are some meditations that may be particularly well suited to this...
- Meditating on the Skandhas.
- Meditating on Emptiness.
- Look for the self.
- Bare mindfulness.
- Choiceless awareness.
- Meditating on determinism (if you don't believe in free will)
The key with any meditation is not to exclude any phenomena. This is key because we can often have blind spots.
For instance, I'm looking at my senses and concepts, yet there's this concept/sense of me looking at these senses, a concept/sense that I don't actually treat as another concept/sense.
Or I am aware of what I'm doing, yet I have a blind spot about my sense of intention as being another sense and instead think of myself as an independent actor acting in the world.
Or I look at external and internal phenomena, while maintaining a differentiation of what goes on inside and outside me (subject and object), instead of seeing it as a flurry of experience, including the experience of classifying these into separate experiences.
Once we really open to all experience, we should end up with a thorough-going non-duality, which erodes all the discrimination which either lead to the sense of self, or that form the substrate of our thinking, the "units" we use to construct (among other things) our sense of self.
In short, any meditation -- properly approached -- should erode this sense of self. The key is to be ruthless about all phenomena, and not to leave anything out.
Still, some meditations may focus more clearly on this sense of self than others.