Re-position the wireless router (or wireless access point) to the centre of the house.
Place the router away from walls.
Place the router off the floor.
Place the router away from metal objects.
Instead of using a standard antenna which you get with the router, use a hi-gain one. If the standard router is placed by an outer wall, part of the wireless signals will be directed outside the house. This will also waste the power of the router. Hi-gain antennas send the wireless signals in a single specific direction which you are able to aim on the path where you need them a large amount.
Replace your laptop or computer's wireless network adapter with a USB network adaptor. It uses an external antenna that improves the range of the signals. (Laptops which have built-in wireless normally contain outstanding antennas. They do not usually require to be upgraded.)
Add a wireless repeater to extend the signal range.
Change the wireless router's channel to increase the strength of its signal. You can do that through the configuration page of the router. The computer will detect the new channel itself.
Reduce wireless interference by avoiding wireless electronics which use the 2.4GHz frequency. You should use cordless phones which use the 900MHz or 5.8GHz frequencies.
Update your firmware updates for your router through the manufacturer's website. Update your network adapter driver through the Windows Update feature of Windows 7 and Vista or visit the website www.update.microsoft.com for Windows XP.
Upgrade 802.11b devices to 802.11g or buy a new 802.11 g equipment. It is five times faster than an 802.11b device.