Head North out of the parking lot through the gate to the trail intersection where you'll see the return route coming in from the right. Drop your daily user fee in the pay box if you don't have an annual membership and take a look at the trail map and kiosk.
The buff singletrack winds through pinion and juniper forest, gradually gaining just over 100 feet to the "saddle". Descend down the Coco Race section; after this twisty descent you'll cross through a big arroyo and then up a short but steep climb followed by a little flat trail for recovery.
At the intersection on top of the next saddle, stay left again for the Lemonhead section unless you are short on time and want to go straight for the Rib Cage. Lemon head Trail goes over a couple of ledges, traverses the hillside and then climbs up to the top of mesa. After a few miles, you'll come to the Cortez overlook which is a good spot to regroup and look West to great views of Totten reservoir and the City of Cortez.
Following Lemonhead is a quick drop into the Maze section. Prepare to get your climb on as you exit the Maze and climb back up to the Elbow section. Elbow takes you across some slickrock.
After the Elbow, the trail returns to smooth, hardpacked singletrack heading East with some terrific views of the LaPlata mountain range. Take a left at the Abajo junction (straight is a shortcut into the lower half of Ribcage) and climb up to the Abajo overlook. It is customary to stop here for a snack and regroup. On a clear day you'll see mountain ranges in all direction including the LaPlatas, the Wilson group, the Abajos near Monticello and even the La Sals near Moab.
From the Abajo overlook, traverse the ridge to the Ledges turnoff going left. For this description we'll stay right and skip Ledges but it is a great loop that you can add on if you have time. Ledges will come back in to the main trail just down the way from where you left it.
Shortly past the Ledges Turnoff, there is an intersection for the Stinking Springs
Loop. If you want to avoid this and get straight to the top of the Rib Cage, go straight.