You hear us but we can't hear you.

You can hear us but we can't hear you.  This usually means your microphone settings are wrong.
Go to Discord settings (the gear icon) -> "Voice & Video" -> "Input Device"
Make sure "Input Volume" isn't extremely low.  We recommend having it at 100%.
Make sure "Input Device" is set to the right device.
If "Default" isn't working, try setting it to the specific device you're using.
If that doesn't work, check if your headphones/speakers have a physical volume control or cutoff switch that needs to be adjusted.
If that doesn't work, QUIT DISCORD completely and then re-run it.  Sometimes it's just a Discord network issue.
If that doesn't work, right-click the speaker icon in your taskbar (next to the system clock) and choose "Recording devices".  Right-click your microphone device and choose "Properties".  Switch to the "Levels" tab.  If the volume is extremely low (below 40%) try increasing it.  If it's NOT low, please don't change it.  That is not likely your problem, and increasing it further is only going to cause clipping, not fix anything.