1. Removed obstacles for me doing a good job - that could be handling politics, ensuring requirements are readily available, logistics of equipment, working space, whatever it may be. Turns out, a good manager handles a trillion seemingly trivial things that add up to being crucial to smooth team operation, but may never be visible to actual team members; kind of like nobody pays attention to Infra until it breaks :S
2. Made themselves available: I now understand the value, and difficulty, in answering "Yes" to every "Hey, got 2 minutes?".
3. Mentorship: it may be advice particular to current skillset, but typically it's more thoughts and frameworks on things I'm not familiar with or above my paygrade: how to work with clients or management, how to approach one's career, etc.
Somewhere between Time & Mentorship, a personal example: in 2011, we had a major document deliverable; every evening, for weeks running, my lead would spend an hour or more going over the documents I produced, making horribly annoying corrections over and over and over again. It took me a long time to realize a) the kind of time commitment this presented on their part - it would be so much easier for them to fix the document themselves than to patiently guide me, but would not have advanced me; and b) how much it made me pay attention to detail, readability, assumptions and scope ever since.