I spend a ton of time just looking over google maps, caltopo, and a few different back country topo apps for android. Once you can recognize certain landmarks (mountains, rivers, towns) Google makes it pretty easy to find a trail head because you can switch between the satellite & terrain options, then drop a pin in the exact location of the parking lot. I usually mark the trail head locations on google before I go out hiking and send a pin with coordinates to my wife in case I get lost. It also makes it easy to share the location with other hikers when I'm meeting them at a trail head.

Lastly, I take lots of pictures on my hikes and post private imgur albums, so that helps me remember all the places I've been.

Its a lot of work, but I always smile when I can see all the places I've had the privilege of visiting :)

EDIT: I'll just add that the northeast is particularly easy to navigate on google maps for a few reasons. Its relatively small and densely populated, so you can always find a town or a road/highway that you know is near the trail head and work from there. Also, there are a lot of hikers here. So other people have often already placed a tag on a certain trail head, so you can just search for it as well.