I posted about this in another thread and thought it might be more useful as a standalone post. Changing the channel your Router/WAP uses can give you a cleaner WiFi signal in congested areas (apartments, dorms, denser neighborhoods).
If you're concerned about wireless congestion, install Acrylic's WiFi Scanner and Analyzer on a wireless PC/laptop, fire it up, and take a look! No, I'm not affiliated with them in any way: https://www.acrylicwifi.com/en/wlan-software/wlan-scanner-acrylic-wifi-free/
Here's a decent write-up on some things that can affect WiFi performance: http://www.howtogeek.com/209450/how-you-and-your-neighbors-are-making-each-other%E2%80%99s-wi-fi-worse-and-what-you-can-do-about-it/
Otherwise, use an Ethernet cable for best results!