1st off, read the other post about the giant horse event at the Coyote Creek entrance. That leaves the HQ entrance for tomorrow. There are two main options. For a first trip, you might want to ride out Manzanita Point Rd, down China Hole Tr to China Hole and up the other side, then return to HQ. It's about 15 miles and under 3k' of climbing. The singletrack is nice and will not feel like you're riding it twice, IMO.
The other option is a Middle Ridge loop. It will be more strenuous, more technical and more scenic. You go left on Flat Frog Tr after the initial descent on Manzanita Point Rd. Flat Frog is awesome, 2.2 miles, not so flat, but no major climbing either. It ends at Hobbs Rd. Climb Hobbs to the top. Maybe stop off and check out Frog Lake below the bathroom on the right. Don't climb Frog Lake Tr from the lake to the top. The no-bikes sign is missing there and you wouldn't find anyone on the sweet singletrack climb to the top, but it's off limits

.
At the top of Hobbs, go down about 25 yards past the right turn onto Middle Ridge Tr to the picnic table overlook of Blue Ridge. It's an awesome spot.
Middle Ridge has two climbs. The first is a real challenge. I made it once. There are two right-hand trail turns, both off-limits to bikes. Middle Ridge has lots of ass-off-the-seat downhill pitches. Try not to skid it up. It's awesome.
At the bottom, cross the creek, ride through the campsite, cross the creek again to the right and you'll pop out on Poverty Flat Rd. Resist ANY urge to go right up the road. It was built by satan himself on a particular bike-hating day.
There are three options from Poverty Flat. After turning left, east, before the creek, on the right, you can find Cougar Trail. It's a very steep 1/2 mile hike-a-bike up to China Hole Trail. It's the fastest way out if you're in a hurry. I used to be able to do the MR loop with Cougar option in 2 hours. It would probably take me 2.5 nowadays.
If you skip Cougar, cross the creek again on the road, continue past the bathroom and on the right, just before the road starts to climb, you'll find creekside tr that starts with yet another creek crossing. Creekside has poison oak. Don't say I didn't warn you. It also has hike-a-bike with a couple spots that are on a hillside with some exposure. Warnings aside, it's very scenic, mostly rideable and a quick way to get to China Hole, so you can climb singletrack back up to HQ. Stay along the creek to the right and you can't miss China Hole and the trail back up. This option adds about 30 minutes vs hiking up Cougar Tr.
The 3rd option is the longest and probably adds another hour and another 1000'. Continue following Poverty Flat Rd uphill, take a right on Mahoney Meadows Rd (*), past Los Cruzeros, up a couple heinous climbs you'll find Lost Springs Tr. I haven't been on it in a while, but it probably has a good crop of poison oak too, but it's a great trail. At the top it meets up with China Hole Tr and Mahoney Meadows Rd again at another bathroom. From there take China Hole Tr down to China Hole and then up to Manzanita Pt Rd.
(*)There's a singletrack bypass here, Schaeffer Corral Tr. If you have a map, take the singletrack instead.
Get a map at HQ. It's worth the $9. Bring more water and food than you think you'll need.
When are you going? All this typing has made me want to go too.