Basic help (No spoilers)

• Keyboard Quick Reference Card v1.2
  (sort of focused on the numpad mode)
• Official Nethack 3.4.3 Guidebook

Tools

• nethack-sokoban, a Sokoban trainer written by appro & oxmox.
• ttyrec is a tty recorder. Recorded data can be played back with the included ttyplay command.
• ipbt (It's Play-Back Time) is a 'high-tech ttyrec player' which analyses the entire ttyrec file before beginning the playback, and reorganises it into a form which permits frame-by-frame forward replay, backward replay and search function.