Digikey has one of the better search engines, not least because you get preview thumbnails of almost everything, and you can search in single unit quantities. It also has some intelligence when filtering parts by value (eg Leds by wavelength).
The problem is usually knowing the names of things, and eventually you learn what keywords to search for eg 2row 10way for a 2x5 connector. Everything is mostly standardised.
Octopart is best for finding stock, I wouldn't use it to locate a new part.
For finding new chips, like random sensors, the best way is to trawl the major IC websites (Ti, Max, etc) and see what pops up. You can still get samples from most of these places, and of quite expensive parts too.
The problem is usually knowing the names of things, and eventually you learn what keywords to search for eg 2row 10way for a 2x5 connector. Everything is mostly standardised.
Octopart is best for finding stock, I wouldn't use it to locate a new part.
For finding new chips, like random sensors, the best way is to trawl the major IC websites (Ti, Max, etc) and see what pops up. You can still get samples from most of these places, and of quite expensive parts too.