Here are some things I do to get around 15+ kmpl in my Civic-AT:
(I used to drive aggressively with my previous car OHC 1.5 and always got around 11 kmpl. When I bought my Civic-AT I was initially getting around only 8.5 kmpl on highways. I was terrified and decided to challenge myself to achieve the highest possible FE. I was also getting older and more matured!. I Read a lot on hypermiling on the net. I was also worried about some accidents that had happened in my family and decided to stop aggressive driving once and for all).
So here goes:
1) I use the car mostly (99%) on highways. (Not every one can practically do this!).
2) I try to hold a steady speed within 67 to 74 kmph.
The AT maintains 5th gear at these speeds.
(My wife and children fight with me to go faster, but I don't

).
Even buses and lorries overtake me! But then I enjoy the stress-free, safe and quite drive.
3) I try to avoid using the brakes as much as I can. (This needs a lot of anticipation and forward planning).
4) I minimize AC usage - when I travel with my family I use the ACC, but when alone I keep the lowest possible manual setting).
5) I keep tyre pressures at 33 psi. I regularly check them and use a foot-pump. (Maybe I can go higher for better FE, but I do not want to sacrifice comfort).
6) When I know a speed-breaker is going to come, I sometimes shift the gear-selector to 'N', so the car 'coasts' to it. (Cars following me may get angry with me for this! ).
7) When there is a fly-over, I try to reach its base at the correct speed so that the car climbs it at 'N' (engine just idling) and go down using gravity! (But this can be done only when there is sparse traffic).
Some more notes:
Since my place is a small town, I can get on the highway within around 4 kms, whereas in big cities you need to go through a lot of traffic and signals wasting fuel.
I go for very long drives without stopping (400 kms) twice a month. Since I avoid short starting and stopping, the engine always runs at its peak efficiency giving better FE.
I always self-drive and do not have a driver.
I think the Civic at rock-steady-speeds uses a lot of advanced engineering to maximize FE.
Finally the most important is motivation!
I keep challenging myself to break my previous FE records.
I maintain meticulous records in a spread-sheet of all my fuellings. (I always fill full-tank).
Here are some more statistics:
In the first year:
kms run: 23,567
petrol consumed:2,243 lts
Kmpl: 10.5 (bad!)
Second year:
kms run: 18,537
petrol consumed: 1,536
Kmpl: 12.0 (good!)
Now I want to push myself to achieve 14+ kmpl in the third year.
(Though I get 16+ on short-term basis, on a long-term (yearly) basis, I might get only 14+).