Level 11 - Sumo Sky Palace (5 secrets)
1. Left side of "door with gold key". Open panel. Get riot gun.
2. USE the red "chair/bench" between the 2 slicing things. It will sink. GO through passage and hit switch on other side to bypass other slicing thing. Get sticky bombs.
3. Opposite secret #2, the other side of wither slicing thing, there are panels that can be opened when USEd. The trick is to do it, and live through it. Just JUMP on the "safe" section of the slicing thing and USE the panel when you revolve round to it. Get guardian head.
4. Lava place with columns moving up and down. JUMP, NOT on columns but on outer perimeter wall and GO around to other side of large rock. Get a lot of stuff.
5. When you CLIMB up a ladder somewhere and there is something shooting fireballs in your face, GO Southwest and BLOW up the crack. Get missiles, sticky bombs, nuke.
Non-secret things to note:
There is a bookcase in the same room as a "pool/Jacuzzi" of green "liquid/acid" that contains a rail gun.
Level 12 - Bath House (5 secrets)
1. (IMPORTANT: Make sure you read this first!) When you approach the green "propane" truck, yes, HIGHLY EXPLOSIVE PROPANE tanks. Make sure you don't hit the tanks or everything will be destroyed and the secret will be inaccessible. (This is the only secret that has this limitation.) Get rid of all the enemies on top of the truck without hitting the tanks. Then go behind the truck to a wall panel marked "Janitor". USE the wall get the medikit. After that you can BLOW up the tanks.
2. In the bathroom, flush (USE switch) the toilet in the centre cubicle. Door on right opens. Get riot gun.
3. Where girl is bathing, USE the "blue towel" (If the "towel" is BLOWN off, and you can't find it, use the coat hanger on the wall furthest away from the girl or if she is BLOWN away too, Sheech! you must be violent! Follow description below.) After going through doorway with sign "Gold Card Members Only" go up stairs. Turn around and face the "door with yellow pass key" you came through (South). Then turn left to the East. You should see 2 coat hangers on a black marble wall use the one on the left.
4. Opposite doorway with sign "Gold Card Members Only", BLOW up statue, etc. Get medikit.(you'll have to go all the way in for the game to say you actually "found" this secret.
5. In "red" room, on North wall, BLOW the crack in wall, GO in. Get night vision goggles, rail gun.
(Source: http://www.pcgameworld.com/ Website)