Re: 156 - when to use 6th gear
you can change from 6th to any gear, such as 2nd, without going through all the gears. its called a block change, your instructor should have taught you that. so if you see heavy traffic ahead you just change diretly into the gear that suits your speed when you change, if you slow quickly then block change down the gears.
which gear you use depends on your speed, the road conditions and the incline. you cant say "'as soon as i get on the motorway" because that motorway may be up a big hill, have traffic doing 5mph, etc etc.
i know you're new to driving but gear selection really is common sense. you select the gear that is appropriate for the speed and conditions. if you're going down a motorway at 70mph then 6th is the correct gear in almost all situations.