Lyric discussion by strider3005 

Cover art for Still lyrics by Foo Fighters

I didn't really get a chance to explain before, I was in a rush. So:

"If you'd like to walk awhile We could waste the day follow me until the trees I will lead the way"

Maybe sung by River Phoenix's character, as it was he who led the gang.

"Bring some change out to the bridge bring some alcohol they will make a final wish just before the fall"

They only took a small amount of money with them, and the alcohol line could refer to them acting older than they were.

"Promise I will be forever yours" The characters made a pact that they'd be friends forever.

"Promise not to say another word Nevermind whats done is done Always was a lucky one"

Maybe them sharing secrets.

"Watch the sunrise all alone sitting on the tracks hear the train coming roaring in never coming back laying quiet in the grass everything is still river stones and broken bones scattered on the hill"

The entire film their journey was along these train tracks - it was like their guidelines, and twice encounter a train (once where one of them wants to jump out of the way just in time, and the second where they crossing a bridge).

"Promise I wont be forever yours Promise not to say another word Here forever deep beneath the dirt Nevermind whats done is done Always was a lucky one"

The same as before, but the "beneath the dirt" could refer to the body they were searching for.