I don't mean polishing the grotty fingerprints and yoghurt splatters, but getting the grime out of the nooks and crannies.
Mine are 9 months old and they're vile - all round the edges of the lenses is gross. When at work I get them quite literally shit up sometimes, and apart from giving them a wee soak in soapy water I'm never sure how to get them properly clean without wrecking them.