Hey, Stp, You sound like you need a good book to read about climbing Mt. Whitney. There are several, although they become obsolete quickly due to the USFS rule changes. Go to Amazon.com and browse around, and read the reviews.
The MR is marked by a sign, North Fork, and it goes up very steeply to enter brush and willows. I can hardly see how people get on this route with the 8 foot wide graded main trail going straight ahead, but I guess some do.
I didn't have a good map my first time, but had studied a topo. There's just one main trail to the top, and the only junction you can go the wrong way is a few hundred yards past Trail Crest (signed) at 13,400'. You can wait for someone to come by, if you're unsure, as there will be dozens all day, if I know this trail and peak.