This is a guide of my collected knowledge and answers to questions I had to scour Google to find. I hope it aids the convenience of others.

To switch to Alternative keybindings, go into Settings > Keyboard > Alternative Setting.

Standard Movement
W - Move Forward
Q/E - Turn Left/Right
A/D - Sidestep Left/Right
S - Step Backward
This isn't the same as backpedaling that we know and love in other action RPGs but is a good way to try getting out of a stagger-lock - or dodge attacks completely.
W + Alt/RMB - Jump
Allows you to climb some low ledges and get a small boost of speed when running - at the economic cost of looking like a flailing idiot. When held you'll bunny hop.
Caplocks - Toggle Walk

Swimming
When in water deep enough you can dive beneath the surface by pressing Alt/RMB. To move around:
W - Turn Down
S - Turn Up
Q/E - Turn Left/Right
Alt/RMB - Swim Forward

You can also use the mouse for controlling your direction, albeit inverted.

Going forward, note that Ctrl can be substituted with LMB in all instances, in the same way RMB can substitute Alt.
Thanks to namelesshero for pointing this out.

Learn to love Ctrl+W because you will develop muscle memory for it. It's basically the A button of Zelda in Gothic. Examples:

Used on..
• an item on the ground; picks it up.
• a non-hostile npc: talks to them.
• corpse: open loot window.
• torch post while holding a torch; lights it.
• cook pan: cooks raw meat in your inventory.

It's also how to equip your gear and use items in your inventory when selecting them.

You'll find chests to loot or store loot inside of - even though your inventory has no limit. At Old Camp, near the arena, there's a vacant shack with two chests that you can use without reprecussions. A nearby npc named "Guy" will direct you to it.

Basics
Tab - Opens inventory
A/D - Cycles inventory columns
W/S - Moves your selection in the column
Ctrl+W - Use selected item
Ctrl+S - Drop selected item

Barter/Storage/Looting
Ctrl+Q/E - Move items in 1 increment
Ctrl+A/D - Move items in 10 increments
Ctrl+Shift+A/D - Move items in 100 increments

Spacebar - Draw/Holster Weapon
Its hotkey number (1) can also be used.
Ctrl+W - Forward Attack
Your bread & butter move, stepping forward while attacking. When you gain weapon training this attack includes follow-up swings.
Ctrl+Q/E - Horizontal Attack
Stationary sweeping attacks. If you get a rhythm both keys can be used back-and-forth fluidly. Weapon training makes this much easier.
Ctrl+S - Block
Cannot be held.
A/D - Sidestrafe
Your character will remain facing the target he's engaged with while strafing.
Tilde (~) - Fight Unarmed
Lets you enter unarmed combat stance without needing to go into your inventory and unequip your weapon. Great for getting Mud to buzz off without angering guards.