How to position antennas for best range

[sponplat]

Hi,
I have an Asus RT-AC66U and I'm wondering about the positioning of my routers anntennas. I have swapped one of the stock anetannas with an 2.4GHz High Gain 9dBi Asus anteanna.
The router location is fixed and is the red square on the added photo. I want optimum connection at the blue square in the basement. How should I point the antennas for optimum range ?
Also, what would be the best positionning for getting maximum coverage (on the same "hight"/"level" as 1st. floor) but straight to the left ?
All walls and floors are wood, not concrete or something similar.


http://imgur.com/JQvsF4x

 

[price_th]

http://www.connect802.com/antennas.htm

https://www.google.com/search?q=wifi+antenna+signal+propagation+patterns&biw=1280&bih=634&tbm=isch&tbo=u&source=univ&sa=X&ei=cBGPVL1vx_uwBJu9gdAP&sqi=2&ved=0CB0QsAQ

 

[nucolos]

I read somewhere that you should put your antennas one at 90º and the other one at 0º, so one facing up and the other one laying down. But you have 3, so i would have the big one pointing to the right.