Hotkeys:

ESC - menu
F1 - help menu
F2 - save game
F3 - load game (single player) / diplomacy (multiplayer)
<~~> or <I> - open/close inventory
<Q> or <B> - open/close spellbook
<W> - open/close quest log (multiplayer only)
SPACE - open/close inventory & spellbook, return to game after death (multiplayer)
TAB - stats/picture mode in info panel
Ctrl+<O> - smoothing on/off
Ctrl+<H> - show health on/off
Ctrl+<L> - flying damage on/off
Ctrl+<W> - change retreat mode
Ctrl+<F> - change formation mode
Ctrl+<N> - day/night changes on/off
Ctrl+<U> - change autocasting mode
Ctrl+<K> - show player names and clans on/off (multiplayer)
Ctrl+<T> - network statistics on/off (multiplayer)
Ctrl+<C> - toggle message color standard/alternative (multiplayer)
Gray <+>,<-> - change game speed
<M> - move
<A> - attack
<G> - guard
<D> - defend
<C> - cast
<S> - swarm (move & attack)
<T> - stand ground
<R> - retreat
<P> - pickup all sacks (for heroes only)
<L> - stand still (do not attack anybody)
<E> - select all of your mercenaries
ALT - force move
CTRL - force attack/swarm
SHIFT - force add/remove unit to selection
CTRL+<1..9> - save group selection
CTRL+SHIFT+<1..9> - save group selection (multigroup mode)
<1..9> - restore group selection
ALT+<1..9> - restore group selection with   screen centering
SHIFT+<1..9> - add group to selection
Ctrl+F4..F12 - set spell shortcut
Shift+F4..F12 - set inventory item shortcut
F4..F12 - use spell/item shortcut
Ctrl+A - select/deselect spell for autocasting
Enter - send message (multiplayer)
BACKSPACE - clear all messages
ALT+F4 - quit game

Entering messages:

BACKSPACE - delete left character
Ctrl+BACKSPACE - delete left word
TAB - player name tab extension
<UP ARROW> - return previous input
[message] - message addressed to everyone in close proximity
=[message] - message addressed to all players
-[message] - message addressed to all allies
-<player's name>[message] - message addressed to a particular player
#kick <player's name> - remove player from the game
#locate <player's name> - locate player
