You go into town. Track down Young Biff and tail him. Sometime today, Old Biff will show up to give Young Biff the almanac.
8 seconds sound clip from the Back to the Future Part II movie soundboard.
You can hear this line at 01:02:47.731 in the Blu-ray version of the movie.
Quote context
[...]
- Jennifer and Einie will be fine, and they will have absolutely no memory of this horrible place.
- Doc. What if we don't succeed?
- Oh, this is heavy, Doc. I mean, it's like I was just here yesterday.
- You were here yesterday, Marty. You were. Amazing, isn't it?
- All right, sunrise should be in about 22 minutes.
- Above all, you must not interfere with that event.
- Right.
- Once Old Biff is gone, grab the almanac any way that you can.
- Remember, both of our futures depend on this.
- You don't have to remind me of that, Doc.
[...]