I often struggle to choose which key use.

To move is quite simple : WASD (or arrows).

But for basic actions such as jump, activate a switch, dash, attack ?

I thought using the letters I O and P at the right of the keyboard.

Have you a better suggestion ?

Which keys are you comfortable with ?

Usually  it will be easier for the player to pick up and play your game if you use standard key bindings. But you as the developer can test your hypothesis to see if your game will work better with different keys!

I'd say the most used are: 

WASD + mouse (if you need more buttons, Q, E, ctrl, shift and space)

Or

Arrows + Z, X, C and space

I usually add both controls as they don't overlap.  As jam game is often played in browser, player usually has mouse in hand so WASD may have the least friction.

Also do use same same input method in menu as ingame.

Edit: The worst key bindings in game I've seen were WASDQE without mouse. My left hand cramped while right hand had nothing to do :D 

I do either:

Arrow keys, Z, X, and space

or

WASD, N, M

Thank you !

I won't be using so many buttons this time (for this jam) but I'm glad to have clear answers.