If one of them doesnt work out for you, I may have miscounted a little, but just lemme know and I'll fix it.
I will not be giving map locations of most pits, just find space for them.
Hopefully this is helpful to you guys who wanna map but are anxious about a starting location.
THESE ARE THE PLACEMENTS OF THE STAIRCASE, NOT THE STARTING SPOT YOU STAND IN.
Level 1 - 4 from left, 9 from top (THANKS SpiderFighter)
Level 2 - 7 from left, 12 from bottom (stairs from level 1) (THANKS SpiderFighter)
Level 3 - 19 from left, 20 from top. (almost center)
Level 4 - This one is tricky, as you will see with the 4 teleporter rooms. As for the starting staircase, 21 from the left, 34 down.
(dont read if you care about the name of the teleporters, no real spoilers here, says right on the wall)
Time and Tide - 15 from the left, 9 down
The Catacombs - 20 from the left, 25 down
Thought whatever - 25 from the left, 29 down
Beast blah blah - 10 from the RIGHT, 2 down (the reason these are important, you'll find out)
Level 5 - 22 from the left, 13 down
Level 6 - 14 from the left, 16 down
Level 7 - 13 from the right, 4 from the bottom
Level 8 - (minor spoiler about how you get down to level 8)
NE Stairs down, 17 from the left, 9 down
SW Stairs down, 9 from the left, 14 down
Level 10 - 6 from the left, 6 from the bottom
EDIT: I'll update this as I beat the game, so you may get ahead of me, if so, feel free to drop the coordinates of the levels once you have them mapped If I dont have them listed.
EDIT2: Updated for level 1 and level 2 thanks to SpiderFighter. Also, level 9.
EDIT3: Updated with level 10.