Open Control Center on your Apple Watch by swiping up from the watch face
Check the battery percentage at the top of Control Center
Add the Battery complication to your watch face for quick access
Swipe to the Battery widget on your iPhone if your Apple Watch is connected
Open the Watch app on your iPhone and check battery status in the My Watch tab
Ask Siri, “What’s my battery level?”
Look for the low battery icon on the watch face when the battery is low