Apple Watch - Getting weight lifting to count towards "move ring"?
Make sure you are using the Workouts app on the watch as this will make the heart rate monitor get your heart rate more often. Therefore, it won't miss any spikes from lifting and moving about.
Make sure your watch is securely fitted so the heart rate monitor can get an accurate measurement!
Lastly, it's a bit hard for a device on your watch to know that you are using weight resistance, etc. so don't expect much. Perhaps we'll see some updates from Apple about this, here's hoping!