few years back i thought the aluminium trick was worthless. recently i got a new N router with rapid internet downstream. the router was wallmounted and the antennas are at close proximity with the wall. what I did was stick 2 aluminium foil sheets on the wall.
ISP downstream plan:100Mbps
Speed acquired from wired connection: avg. 80Mbps
Speed acquired from wireless N: avg. 50Mbps
Speed acquired from wireless N with alumunium foils: avg. 60Mbps
i recommend this for those who have their routers wall mounted, because it only takes minutes and the speed gain is quite worth the effort. i believe alumunium can will be a better candidate for this project.