This is the "main loop" that many riders take with various add on sections and lookouts.
There are various trailheads to start at. This description starts at the Genser trailhead behind the Starr Pass Golf Resort. There is ample paved parking at the trailhead. This ride starts climbing immediately on a rocky trail. As you head out there are two areas that lead off to the left. Stay to the right on the main trail. It's not too steep and if you can make it over the rocks the first difficult part is at the first set of switchbacks. Stay to the outside of the turns to ensure you make them without stepping down.
After this, the trail goes down to the 4-way, where there is a sign. At the 4-way make a left. This section is steep, rocky and you can get going fast. Watch your lines, and watch for riders coming up the trail. At the bottom of the steep section, the trail splits. Stay to the left. Shorty thereafter you'll come to another intersection. Head straight. The trail drops down to the wash. If you aren't watching, you can go down to the left and end up in the wash. It's rideable, but not as fun as the trail above.
Make sure to make the right up the hill before heading into the wash. The trail from here takes you to the pass. Once at the pass, continue straight and drop down. In the wash you'll see the trail go off to the right or straight. Either way will get you to the same point, but the right is harder. The right takes you down and up some steep whoop-de-doos. At the end of them you'll get to an opening in the fence line.
From here take a right. If you take the easier route down the wash, it takes you down to a gate. From there take a right up the access road to the opening in the fence. Continue on the access road and it will take you to the next gate. On the other side of the gate the singletrack continues to the left. The trail is more of what preceded it, rocky and heading up and down singletrack.
The trail comes to a clearing and continues heading to the right up an steep slightly technical section. At one point on the way up, the trail splits in two, but both ways lead back together, choose either direction. Once you get to the top, the fun new section of downhill singletrack, avoiding riding the wash, awaits you. From here you head back up to the same 4 way that you saw at the beginning of the ride. In order to get there, stay left at all intersections. From the 4 way head right and retrace your tracks from the beginning few miles of the ride.