'Except' means 'Not including': They were all happy except Jane. After words like all, every, no, everything, anybody, nowhere, whole etc., 'except' and 'except for = apart from' can both be used with the same meaning. 'There was no light except (for) the occasional glow of a cigarette.' 'They all came except (for) him.' We use 'except', not 'except for', before prepositions and conjunctions: 'They live in a remote area, inaccessible except by car.'

Ok, native, but not versed in grammar. They do nothing ____ complain all the time. Cannot use "except for" I did everything ____ the last exercise. Can use either He's not very friendly ____ when he wants something. Can use either. Everyone was there ____ Kumiko. Can use either. There was complete silence ____ the sound of someone coughing. Can use either. I have no answer to the criticism, ____ to blame the short-sighted management. Cannot use "except for". They have no one to blame for the trouble ____ themselves. Cannot use "except for". Sorry, I cannot see a neat rule.