I've found that Active, which is the default, is pretty useless as it tends to be a self-fulfilling prophecy sort of thing. Everyone sees the most active stuff and they become more active, keeping them at the top.
Hot works better for a balance between New and Active.
I recommend changing your default sort in your settings to anything but Active. While you are there, might want to change the default grouping from All to Subscribed.
Oddly enough, Active has been the best for me. When I sort by Hot, I get almost entirely 2+ year old posts. Guess it all depends what communities you've joined
Hot is good but it works more like "rising" on reddit did. I sort of go between hot and top 6/12 hour for a combo of rising things and things that have a lot of interaction but aren't stale.