What are the original controls of Doom (1993)?

← to turn left
→ to turn right
↑ to move forwards
↓ to move backwards
Alt + ← or → to strafe
Ctrl to fire weapon
Space to use (open doors and use switches)
Shift + movement keys to run
1 - 7 weapon selection

Taken from the original game manual, page 9:

F1 = this menu.

Controls Screen Doom v1.0 – The Cutting Room Floor

In FPS games of that era, players were not expected to (and in the case of doom, could not) explicitly aim vertically, they just had to aim horizontally and the game would take care of the vertical component.

The default control setup in many FPS games of that era (at least, Wolf3D, Doom, Duke3D, and Quake), revolved around using the right hand on the arrow keys for moving forwards/backwards and for turning. Other important controls were typically in locations intended to be convenient for the left hand, often on modifier keys (presumably to minimize the possibility of key rollover issues). Weapon selection was on the number keys, which was easy to remember, but not so convenient to press.

In the case of doom specifically, the arrow keys were used for moving/turning, control was used for firing, alt was used as a strafe-modifier and space was used as the activate button. "," and "." could also be used to strafe with a single key press, but this seems like a bit of an afterthought and was not mentioned in the manual.