Using data from the POH, I made my own little A6 weight and balance forms for the two a/c I fly. With experience I found the weight calculation vital under some circumstances (eg full tanks, 2/3 or more heavy males) and the CG less so. For every flight other than solo or 2 on board with half fuel, I scribble down the weights onto my form and add them up to check I'm within the T/O and landing limits for my a/c. If the config is slightly different (couple of cases of wine to bring back from France) then I do a full CG calculation too.
If anything happened, even through no fault of one's own, this is the first thing the AAIB would be doing. If you're too lazy to know where you are in relation to the MTOW of your plane, what other shortcuts are you taking?