Pause and resume the download
Change the download region in Steam settings
Clear the Steam download cache
Limit bandwidth usage in Steam
Disable VPN or proxy
Close other apps using the internet
Restart Steam
Restart your router and modem
Use a wired Ethernet connection
Disable background downloads on other devices
Check for Steam server issues
Make sure the drive has enough free space
Install to an SSD if possible
Temporarily disable antivirus or firewall restrictions
Update network drivers
Change the download schedule to off-peak hours
Verify there are no Windows updates or system downloads running
Reinstall Steam if the problem persists