for any driving the key to better MPG is anticipation and forward planning.
1,500 rpm is fine on a flat piece of road, but you do need to be aware of and avoid the engine labouring.
Yes move move the gears early, but don't necessarily accelerate fast to allow this.
See junctions, eg roundabouts ahead, judge it so you don't have to stop.
Try not to use the brake. challenge yourself how far you can get on a drive without needing to use it. This will teach you a lot, you will be surprised how much time you can spend off throttle instead of on throttle or brake.
When slowing down, leave in gear.
On roads with uphill/downhill sections allow the car to gain on the downhill so you don't have to powder so much up the next incline.
Parking, don't drive round for 5 mins to save 1 min of walking.
I cannot stress how much anticipating the road ahead helps MPG, but you still need to be careful with the right foot.
also understand what economical speeds mean. many say 56 mpg is the optimal speed, but in reality driving at 50 will get even better mpg. high gear with minimal throttle is good.
motorways, mpgs drop of significantly the faster you go. The truth is that 80mpg is simply not economical. in fact as soon as you pass 60 its a case of increase = decrease in MPG.
servicing too.
engine warms up as it should?