The best method for increasing average of hybrids is pulse and glide method. Check the link and use it :
Driving technique: exploring 'Pulse and Glide' - MetroMPG.com
Pulse and glide works like this: let's say you're on a road where you want to go 60 km/h. Instead of driving along at a steady 60, you instead accelerate to 70 (that's the pulse), and then coast in neutral with the engine off down to 50 (that's the glide). That's it. Rinse and repeat. And repeat. And repeat...
By doing this, you're still averaging 60 km/h, but it turns out that pulse and glide is significantly more efficient than driving along maintaining a steady 60 km/h.
If you're like me, it seems completely counter-intuitive. You're asking, "how can that possibly be more efficient than maintaining a steady speed in the highest possible gear?" After all, it violates one of the main commandments of efficient driving: conserving momentum.
Please note that doing engine off is extreme technique it can be replaced with engine on but lifting your foot off the throttle completely.