These are some common troubleshooting steps if you're having issues with your internet connection.
Reboot Your Equipment
Rebooting involves turning off your internet equipment by unplugging the power, waiting 15-20s then powering back on. It can take a while for the equipment to come back online.
Reboot the Device Having Issues
If you're experiencing connectivity issues on only one of your devices, it could be the device that is having the issue. Try powering down you device for 15-20s and powering back on. Be sure you are fully powering down your device (not just putting to sleep).
Consider How Many Devices Are Connected at Once
The bandwidth you receive with your internet plan (download and upload speeds) are shared by all devices in your house. If you have a device using up a large portion of the bandwidth, this leaves little for your other devices.
Check Your Router Placement
Be sure your WiFi router is not being obstructed. Your WiFi router should be placed near the middle of your home, away from reflective surfaces (mirrors, water, windows, steel appliances), and away from obstructions (don't leave your router in a cupboard or behind a TV, it should be out in the open).
Are Other Devices Interfering?
Have you added a new wireless device, or moved a device in your home such as a weather station, baby monitor, microwave, cordless phone? Many of these devices work on the same frequency as your WiFi and can interfere with the signal.
How Are You Testing Your Speed?
When you're doing a speed test, be sure to be testing over a hardwired connection (connect a device with an ethernet cord directly). Speed tests over WiFi can show slower speeds depending on how far you are from the router, interference, etc.
Check Your Cables
Make sure all the cables are connected. If you have pets, check to ensure they haven't chewed the cabling.