Collective nouns
Most groups, companies, organisations, etc take a singular verb: Boots is opening a new branch; the committee has reached a decision; the Government says it (singular pronoun) will respond when it has considered the matter more fully.
Four common exceptions are the police, staff, and the names of bands and sports teams: The police are reviewing their attitude to race; the staff go on an annual booze-up; The 1975 have released a new album; Scotland are out of the World Cup (again).
That/which
To decide whether a clause should begin with that or which you need to know whether the clause is, or isn’t, a defining clause.
A defining clause is integral to the meaning of the sentence: eg Food that contains too much salt is dangerous to our health. If you removed the clause that contains too much salt you would be left with the nonsensical sentence Food is dangerous to our health.
A non-defining clause is parenthetical, could be cut without making nonsense of the sentence, and should begin with which: Salt, which lurks in sweet foods as well as savoury, is dangerous if taken in excess.
Note that non-defining clauses are put between commas, whereas defining clauses are not.
Or put another way: that defines; which describes.
Tense
In the reporter’s voice almost all news writing takes the past tense. Almost all feature writing takes the present tense.
Do not alter the tense, though, of reported speech.
