removing unused packages
 

is there an easy way to figure out what packages are useless/unused and can be removed?

Well, you can use pkgtool to see their descriptions and remove them. I dunno what would be useless for you so i can't tell which ones you should remove. I personally installed slack selecting each package because i like only installing what i need (it took a few hours to do that...)

yes pkgtool is the thing you need to uninstall packages of slack. useless i would say, things which are doube. like to different audio players, just keep the one you prefere and get rid of the other. and if you will never bother with things like setting up a server you can get rid of that stuff too.

if you really want to save some space, dump your man and info pages and the html documentation. when you finally decide you need it, you'll know and keep it. you can always get that stuff online anyway. and search for stuff specific to languages you don't use. you can get a third of the space back in a system doing that kind of stuff. it seems horrible to someone like me who uses man pages all the time, but newbies don't understand them, so they do little good.