1. Open Network and Sharing center
2. Click on change adapter settings and find your wireless network adapter
3. Click Advanced Settings
4. Scroll down and set Maximum Performance to highest in "Wireless adapter properties settings"
5. Press OK then exit

OR

1. Go to the device manager
2. Select your wifi card
3. Go to Properties
4. Set "Transmit Power" to maximum, and "Roaming Aggressiveness" to lowest setting

Aggressive roaming settings can cause the card to try to switch access points in environments where there are many wifi networks present - often in office buildings with multiple businesses on same floor, or in apartment buildings. Increased transmit power can help with some trade off for run time on battery.

*You can also set roaming aggressiveness to high to search for an access point with a better signal.