I parked my bike at the marina and went inside to get info on the trails around the lake. There are at least two trails in the park, the Kingfisher and the Rookery. The Kingfisher runs along the east side of the lake and begins north of the Marina.
Update 2/2014: I believe it now goes around much of the north and west sides of the lake.
To get on the Rookery Trail, I crossed the road and walked south to the covered information sign. This trail was hard to follow at times, but keep an eye out for light blue blazes and pink and orange flagging. A few words of advice:
1. A the first big open area, walk straight across the clearing and then look for blue blazes on the other side.
2. At the second open area, after the second cattle gate, walk slightly to the left past the picnic table to the other side of the clearing to find the trail again.
3. After the second clearing, the trail enters a wooded area and heads up a hill. Be on the lookout for a gate in the fence (shown below). If you miss this, you'll miss some of the most interesting parts of the trail (and you'll be lost).
4. This later section of this trail follows a VERY long rock wall which I hypothesize to be the long-lost ancient remains of the Great Wall of Arkansas.
5. This is probably the most interesting trail I've been on in Fayetteville since moving here in August. It is also probably the most difficult to follow.
6. Wear good boots, the trail can be muddy and torn up by cattle in places, but the parts past that are worth it.
View Lake Sequoyah Bike Hike in a larger map