My missus buy presents throughout the year, she sees something she thinks someone will like she'll get it and put it in a box, things have been bought in January sales for the next December. That is far too organised for my liking, I've very much a last minute gift buyer - tricky as I live in a small village / town so have to pretty much rely on online gift buying. Although as a rule I'm not fussed about buying gifts really, just try to make to occasion memorable buy doing something fun and exciting.
The things my kids remember haven't been the toys and electronic stuff they've got but the places we've gone and stuff we've done, usually on an impulse - chuck it in the car and go type outings.