Clear Cache Regularly
Over time, apps accumulate cache which can slow down your Firestick. Go to Settings then Applications then Manage Installed Applications, select your IPTV app and choose Clear Cache. Do this weekly for optimal performance.
Free Up Storage Space
The Firestick only has 8GB of storage. Uninstall unused apps and clear data from apps you rarely use. Go to Settings then My Fire TV then About then Restart to keep the system fresh.
Use an Ethernet Adapter
WiFi can be unstable especially when multiple devices are connected. Amazon sells an official Ethernet adapter for the Firestick. A wired connection provides more stable streaming and reduces buffering.