My trick is to make the objects "stand out". Black headphones, smartphones, keys etc are easily overlooked in work bag pockets or when placed on other dark surfaces.

I've greatly improved the "retrieval interval" of my phone since I've put it in a mint-green case instead of the standard black one. Same goes for my bluetooth headphone case, on which I applied reflective stickers.

Another trick is to group related objects. My office key card is in the cover of my work smart phone, so I have to look out for one item less each morning.