Gather the Active Internet Connections

netstat -tnlp

--and
netstat -an

--and
netstat -tulpn

Check memory usage

free -m
--or
free -h

Check process tree

pstree -p

Compress a file/directory

tar -czvf /<path>/to/archivename.tar.gz --exclude archivename.tar /<path>/to/<your file or direcotry>

Decompress a file

tar -xzvf /<path>/to/archivename.tar.gz -C /<path>/to/<your direcotry>

find file recursively

find . -print | grep -i "<target_string>"