Signal strength can have a lot to do with where the router is compaired to where you sit at your pc/ laptop. If you have a house with thick walls you should go for a N type router rather than the G (standard router type). but a simple way to boost signal is to put a pice of tinfoil behind the anntenae of the router, directing the signal to where your computer is and not letting it just dissipate into the walls of the house in all directions.
hope this helps, but remessage if I have not been clear enough ;)