Lugging is when you let the rpm's get too low in a certain gear . Keep it over 2100 rpm's in 3rd , 4th , 5th , and 6th . The 07 is a stroked motor keep the R's up and you and the bike will be happy.
go on an uphill ride ............start out from the bottom of the hill in first gear ,then when you hit 3,000 rpm shift directly to 5th or 6th gear ............
you will learn quickly BUT................DO NOT DO IT FOR MORE THAN SAY 2 SECONDS OR YOU MAY DAMAGE ENGINE.
so , if now you get it ,to lug an engine is to run a certain speed at an rpm that is too low for the engine tranny to mantain power and acceleration..........thus ,you are lugging the engine .and possible damaging it .