Global shortcuts to control playback when using other applications can be set in the 'Shortcuts' panel of the preferenes..
The following shortcuts are available in the main tracks table.
Return — Play from selected track.
Command + Return — insert selected tracks at start of queue and play.
Option + Return — play selected tracks after current track.
Shift + Return — add selected tracks to the end of the playback queue.
Space — Pause / Resume.
Backspace or delete — remove track.
Backspace or delete + command + shift + option — Remove track from the library when viewing playlists.
Control + a number key (0-5) — change the ratings on the selected tracks.
Command + N — select the next track.
Command + P — select the previous track.