Following your advice, I had a 130 mile trip yesterday mostly freeway and I'm happy to say I got 46mpg I think the most help was shifting from 1st, 2nd, to 5th as soon as I reach that 40mph sweet spot. Also, when cruising on a downhill slope, I take the car out of gear and and leave it on neutral until I reach close to the bottom of the hill then pop it back into 5th.
There you go, I've had plenty of practise driving economically, so i'm more than willing to share my ideas and theories. Keep practising, i'm sure you'll get more MPG as time goes on. People don't realise how much a car's transmission will slow a car down, in neutral you're using a tiny bit of fuel for idling, and the rest of the magic is down to gravity!