In questions direct or indirect be careful to use whom when the objective case is required. Do not say, Who did you see there? or, I do not know who he meant.
The relative who should be used only of persons (or of beasts or things personified). Do not say: The dog whom you saw or He drove the horse who made the best record. The relative which should be used only of beasts and inanimate objects. Do not say: The women and children which were numerous then came trooping in.
The relative that may be used regardless of gender and the antecedent.
That should be used after a compound antecedent mentioning both persons and animals or things, as, The soldiers, the ambulances and the pack mules that were recaptured, were sent to the rear.
Be careful of the case of who if a parenthetical sentence intervenes between it and its verb. He said that Gen. Harrison, whom, everybody well knew, had long been interested in the case, would make the closing argument. Such faulty objective is often heard in daily speech and not infrequently gets into the papers. Of course who should be used. But whom should be used when the infinitive follows: He said that Gen. Harrison, whom everybody admitted to be profoundly versed in the law, would discuss the point.
It is proper to omit the relative pronoun on occasion when it is the object of the following verb, as He was among the men (whom) I saw.
CONJUNCTIONS
Never use like as a conjunction. John may look like James or act like James or speak like James, but he never looks, acts or speaks like James looks, acts or speaks; he never looks like he wanted to do something, nor conducts himself like he thought he owned the earth, or like he was crazy. Like (as in the first example) may be followed by an objective case of a substantive, with which the construction is completed: You are like me in this; You, like me, believe this; He conducted himself like a crazy man. When a clause is demanded, as if should be used: He looks as if he wanted something; he acts as if he were crazy.
Do not use if for whether in introducing indirect questions: I doubt whether (not if) this is true; I asked whether (not if) he would go.