2. Fix Any Interference (Free!)
Before you hit the shelves or online stores, you need to make sure interference from other Wi-Fi networks or other transmitting devices aren't hindering your signal.
Neighboring wireless networks on the same or overlapping channel, nearby 2.4GHz wireless devices (such as Bluetooth adapters, cordless phones, baby monitors, wireless cameras, wireless keyboards or mice, and wireless speakers), and even microwaves can cause your signals to reduce or drop completely.
Walk around your home or office and look for anything wireless. If signal problems arise sporadically, make sure you do a walk-around while the problem is happening. If you find suspect devices, disable them, at least long enough to see if it's the cause.
To check for possible interfering Wi-Fi networks, you can download NetStumbler, a program that will show you all the networks in the area (regardless if "hidden") along with their details, such as the signal strength and channel.
Open NetStumbler and let it capture all the networks, preferably on a laptop while you walk your building's perimeter.
If you find a network that's four or fewer channels away from yours (such as channel 4 if you're on channel 1), you'll want to move to the best non–overlapping channel: either 1, 6, or 11.
If there are several networks, pick the best non–overlapping channel, taking into account the signal strengths. To change your wireless router's channel, log into its web-based control panel with the IP address and find the basic wireless settings.