Gradings appear to me, to be something to massage one's ego, whilst masquerading as a safety tool. Half the time they are utterly nonsensical without allowing for the various styles of authors, let alone rain, heat, seepage, etc.
I basically look in a guidebook these days, to see if I can possibly get up a cliff or crag and then go and have a crack at it. Steve Ashton's written portrayal of distance is as definitive as "42", so I tend to just ignore it until after a scramble and then see if what I've done matches a description. It worked well last Autumn in 'Little and North Gullies' on the east face of Tryfan, it was a case of looking for a line that both of us fancied and just heading upwards. The fact it had a name and a grade was irrelevant, a Grade 1 as it happens, and wasn't something we realised until we were sat in the pub.
I'me coming to the conclusion that climbing grades are even worse.