I feel HH's are one of the most important tools we have as a player to confirm you are taking the correct measures/steps etc to better your game.  Its amazing how often I say “what the heck was I thinking” when I see a spot play out or a line I take in a hand.  Another tool we have that I use often is Flopzilla.  I spend roughly an hour or 2 each week plotting out scenarios with board textures vs ranges to see the equity and how things change on each street.  I use Word to make notes on what I would do with certain parts of my range as a cbet, as a check/call, check/raise or check give up.  It looks like this:

Hand #1: Board: Ad, Js, 4s

Range:

UTG – MP: All Pairs, ATs +, AJo+, KTs+, KJo+, QJs+, QJo+, JTs+ (14%)

CO, HJ, BTN: UTG –MP Ranges + A9o+, A2s+ K7s+, K7o +, Q7s+, Q7o+, J7o+, J7s+, T7s+, T7o+, 97s+, 97o, 86s+, 86o+, 75s+, 64s+, 54s+, 43s, (40.6%)

Hands we are betting for value (all positions): AA, AK, AQ, AJ, A4, JJ, 44

Hands we are bluffing with:

UTG – MP: KQss, KTss, QTss (Maybe KJo, QJo, JTo)

CO, HJ, BTN: UTG – MP Ranges + K9ss, K8ss, Q9ss, Q8ss

Blinds:  UTG – MP Ranges + CO, HJ, BTN ranges + Kxss, Qxss, Any Spade combo