In the good-old days on the 744, F25 was the standard landing flap. F30 was only used for shorter runways (such as Kai Tak 13), since it resulted in a higher fuel burn.
However, we also used to fly Vref +10.
After the 19th hole incident in BKK by a southern hemisphere airline, we went to a standard F30 landing with a Vref +5 (with corrections).
For take-off, it is F10 or F20 based on weight - runway - environmental performance etc.
For the 777.
Landing is Flap 30, with Flap 20 for S/E.
Take off is normally F5, with F15 or 20 at higher weights and with tailwinds etc.