What is your role within the company?

Beware of the Halo effect [1]. For example, people are biased towards their first and last impression. That's why you/everyone should write stuff down regularly, so you can at least try to offer more objective and balanced feedback, and not just on the first thing that comes to mind.

I would recommend the book "Managing Humans", which originated from a blog [2]. It has good content on how to talk to people, and which mistakes to look out for. I found it quite entertaining. I believe you can read all content online.

[1] https://en.wikipedia.org/wiki/Halo_effect [2] http://randsinrepose.com/archives/youre-not-listening/