Travel in groups
Needs to be qualified by warning of those operators that don't accept Group Save, e.g. CrossCountry.
Buy in advance
Needs to be qualified that they are only valid on specified trains. Recent experience on South Western on a Saturday suggests that a lot of (unhappy) people do not understand that.
The introduction of the penalty fares regime was accompanied by a poster saying "It has never been easier to buy a ticket" should have been re-worded "It has never been easier to buy the WRONG ticket"