I was asked yesterday by a member here on how I store my lego parts.  I usually store them in 3 major group/category:
GROUP 1 -

Conventional sized bricks , plates and slopes and parts of same color goes into one tray. Below are the trays with colors I'm currently using for my MOC project (the rest are in store room)



GROUP 2 & 3

- Group 2  are specialised parts like tyres and joints which I only required a few for my MOC (so I handpick what I need from storeroom)

- Group 3 are special parts like  "stick plates" more than 2 stud long  , or more slopes  (<< just recently sorted them into one tray, since LEGO been introducting alot of these rounded slopes the last few years)



GROUP 4

Trays of smaller ,specialised LEGO parts (gotta isolate them or else hard to korek from GROUP 1)



^  from the top
tier 1 - tiles or parts with no studs on top
tier 2 -  1x1 bricks/headlights/rounded parts
tier 3 - technic parts / pins / connectors
tier 4 - mostly tiny parts goes here  ( 1x1 plates / cheese slopes /tiles) , 1x2 plates



^  from the top
tier 1 - bigger technic parts, bricks with holes
tier 2 - 1x1 or 1x2 brick with holes
tier 3 - wedge plates . (for those with opposing sides, I connect them together as pairs)
tier 4 - brackets
tier 5 - hinges
ps: as you can see.. sometimes the parts are sorted incorrectly. dont care too much since its tedious trying to be systematic.