Hi I ahve done little study in the field of wireless fidelity and antenna propagation.I am electronics and communication Engineer by profession.
What ever I am going to say now is purely theoritical and I have personally not used any wireless access point (though dying to do so.)
Coming to the theoritical technology, here is how it works,
The propagation of antenna signals field strength is in the form of a hexagon.The field strength is distributed in the form of a irregular hexagon.Hence you would have varing field strengths even though you are close to the wi-fi router.
the following equation is called simplified pathloss equation.
Pr=Pt*K*([d0/d]power of r)*g
Pt is the transmitter power
Pr is the reciever power.
where r is gamma
k is a constant
pt is transmitted power
d0 is standard distance
d is the distance from the antenna and reciever(your laptop).
g is called log normal shadowing constant.This is more are less climate and area dependent,this is major contributing factor when obstacles or high rise buildings or high trees are there.
r = 2 if it's free space and
r= 4 if more attentuation is there.
r increases as more dense fields like if you go underground or deepwater.
As pointed out by TJ, it best works in line-sight path, lot of variables get away once you have line of sight,thus helping the field strenght of wirless signals.
Try to have your router, in places where it could distribute it's field strength in circular way.If you put high up it will distribute the field strength in conical way thus helping but it may not serve you if you division of various floors.
For further understanding of wave propagation please refer to Prof.Adrea Goldsmith Articles at Stanford.I find them very useful and simple to understand.
I hope this helps in you some way,
It was nice question and for once I got back to my interest.