If like me you have trouble focusing your laser I would like to share a tip which works for me.
I bought some black aluminium business cards (not anodized just thin black plastic coated ones sold in packs of 50 from Amazon). I place one of these on top of whatever material I want to engrave, set the laser override power to 5% in t2, put on my goggles, activate the laser and adjust the lens focus in small increments until the blue dot starts to turn red and starts burning off the plastic coating on the business card. That usually results in a very fine focus and is good to go.
Hope this helps somebody.
Just to add 'Focus' makes all the difference in the world. Wood is reasonably forgiving (except when going for detail in greyscale) but anodized aluminium or mirrors for example can simply not engrave at all if the focus isn't sharp enough.
Anybody else have any focusing tips to share?