please help - how to check engine fault codes (w124)

well my 1994 E320's Check Engine light came on and I used to have a set of steps to follow to check my fault codes, but I'll be darned if I can find it.
I have a list of the codes, but I don't know how to check/clear/check again the codes under the hood.
I know I have to have the engine on, but I don't know how to do the rest anymore.
This time I SWEAR I'll put it in a doc on my hard drive and I'll never lose it again.
Please help.

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