As it appears on the park map, the Blue Trail is a single loop. But, the Etowah River runs through that loop and it's often pretty deep with swift currents. Unless your bike floats while you swim, maybe wait for a dry spell and a warm day to attempt the loop in its entirety. For this reason, the trail is divided here into North and South sections. The Blue Trail (North) makes for a pleasant out-and-back if the Etowah River is impassable. However, you'll probably still have to get you feet wet at the Shoal Creek ford.
From the parking lot, travel east following red and blue blazes. You'll join the entrance road for a few hundred feet and then take the well-marked turn to the left through the field.
Then you've got about one mile of easy forest road before taking a right up a difficult, rutted singletrack climb. You'll pass through a section of forest that was logged in winter 16/17. They've re-established the trail, and it is marked with red and blue ribbons. After the logged section, the trail returns to singletrack as it switchbacks its way down into a creek valley. The trail then parallels the creek climbing gently for about one mile. This segment ends at a forest road (Powerline Road).
Turn right and then left at the T-intersection with Shoal Creek (forest) Road, always following the blue blazes and signs. Descend one mile on Shoal Creek Road. It should be possible to ride across the Shoal Creek at this point even after a heavy rain, but you may find water halfway up your calves. After fording Shoal Creek, climb Shoal Creek Road for about 1/2 mile and then there is a singletrack entrance on your left.
The next 1.5 miles are typical North Georgia singletrack, gently undulating through the forest with lots of roots, the occasional fallen tree (which you may have to dismount to pass over/around), and a number of shorter creek crossings. After a steep climb, you'll turn left onto North Gate (forest) Road.
After about 1/10th mile on North Gate Road, look for singletrack on the right. This begins a fun mile of singletrack high up on a ridge after which you'll enjoy a quick 200 ft descent down to the Etowah River. Then the trail follows the river for a mile until you reach a trail junction. Here you have the option to ford the river to continue on the Blue Trail (South)
, to travel north on the Yellow Trail
(North Gate Road) back to the Blue Trail (North), or to turn around and backtrack the way you've come.