When critiquing another's writing I find myself making suggestions that are clearly biased toward how I would write the work. This effect seems particularly prevent for poetry, where suggestions are clearly biased by my preference for regularity (especially in meter), certain emotional expressions, and imagery and oblique references. (Poetry also tends to have a density of expression that justifies detailed analysis and a personal character that makes preferences easier to feel and more dangerous to express.)
Part of the problem is disentangling my own preferences from a more general perception of quality. My suggestions usually seem to provide general improvement even when I can clearly see that they are strongly biased by my own leanings.
While declaring my bias would help avoid imposing my preferences on a less confident writer, I think it would be helpful indicate in what ways suggestions lean toward more general quality improvements. However, I may not easily discern why I prefer a particular rephrasing beyond my own biases. Sometimes providing more than one rephrasing suggestion would help, allowing some variation in style or tone, but such does not seem practical for verse.
What are some disciplines and techniques to help avoid imposing my biases while still giving effective criticism?
While I also have significant biases in non-fiction in terms of organization, tone, and other aspects, it at least seems that I can more readily disentangle these preferences from more general quality concerns and to some degree accept different tones than I would prefer.
I suspect broader reading would help, but my motivation for specifically reading things I do not like is low.