From the lower trailhead parking area (the one with the outhouse/restroom), continue west on the 4WD road that leads to the upper basin. After approx. 100 yards, pass a large rock and stay right at a junction. Follow the road 3/4 mile 11,700' where the road gets worse.
Note: You're initial goal is to reach Blue Lakes Pass and there are two different trails that will get you there: 1) the directions described below or 2) Just above 11,700' on the road, at a switchback, there's a marked trail that leaves the left side of the road and climbs up to Blue Lakes Pass. It's used frequently and passes Wrights Lake along the way. The remaining route description will use option #1...
It's another mile to the upper Sneffels trailhead, but the remaining road is rough and should only be attempted by 4WD vehicles with good clearance and a short wheelbase. Continue up the road. On a flat spot near 12,300' (Photo #1), stay right at a road junction and continue the last 1/4 mile to reach the upper trailhead at 12,460'.
From the upper trailhead (Photo #2), hike northwest across talus on a good trail. After over 1/4 mile, reach a trail junction near 12,600' - Photo #3. Stay left and continue towards Blue Lakes Pass - Photo #4. Follow the trail west toward the slope below Blue Lakes Pass and over some talus at the end of the basin. Locate the trail as it starts to climb the slope and begin your ascent to the pass - Photo #5.
Once on the pass (Photo #6), turn right (north) to see the Southwest Ridge - Photo #7. This is a good place to re-tool for scrambling and put on your helmet. Follow a faint trail up to the left side of the rugged pinnacles at the base of the ridge and continue on loose, Class 2 terrain next to the pinnacles - Photo #8. Beyond the first set of pinnacles, locate a gully (Photo #8 and Photo #9) along the ridge crest which is used for the next section of the route. Continue to the gully and begin climbing on sharp, somewhat-loose rock - Photo #10 and Photo #11. After over 100' of climbing, turn left (Photo #12) and continue in another short gully - Photo #13. After a short distance, ascend steeper rock to exit the gully on its right side (Photo #14 and Photo #15) and reach another section of loose rock near 13,400' - Photo #16. Angling slightly right toward the ridge, climb this rough patch to reach a small notch (Photo #17), near 13,500' on the ridge. Blocking your route is a large pinnacle along the ridge crest and it's easiest to bypass it on the right. Photo #18 looks back at the small notch after passing through.
Drop less than 50' toward a defined gully (Photo #19) and turn left around the steep rock (Photo #20) to see the top of the gully (Photo #21) and a much larger notch. Taken from high in Yankee Boy Basin, Photo #22 and Photo #23 show the location of the gully and notch on the ridge. Climb to the notch (Photo #24) and turn right to see another steep, narrow section of rock on the north side of the notch - Photo #25. Climb the short pitch to reach easier terrain above - Photo #26 looks back over the area. If you take the standard line, the remaining climb will be easier than this short pitch. Next, enter a short gully on the left side of the ridge - Photo #27. Climb about 50' and locate a narrow exit (right) that leads to easier terrain on the ridge crest. Just before you exit, there's an interesting rock formation back to your left (west), called the "Kissing Camels" - Photo #28. It's easy to miss the rock formation if you're not looking for it. Exit right (Photo #29) to reach the ridge crest, near 13,700' - Photo #30.
It's less than 500' to the summit, but plenty of fun climbing remains. Bypass an initial pile of rugged rock (Photo #31) and scramble back to the ridge. Climb a bit more and you can finally see the summit - Photo #32. Continue along the ridge crest or just to the right. Near 13,900', reach a steeper section of the ridge (Photo #33 and Photo #34) which contains plenty of grippy, stable rock. The remaining ridge climb has a bit of exposure on the left and some people may prefer to stay just right of the ridge. Either way, the views are excellent and the climbing is fun. Photo #36 looks down from just below the summit. Continue on the good rock to reach the summit - Photo #37 and Photo #38.