Take I-90 to exit 32 (436th St), and turn south on to Cedar Falls Road. Follow it across the South Fork of the Snoqualmie River, up the hill, and on to Rattlesnake Lake, about three miles.

Oops, forgot to mention that there are two (!) trailheads. For the traditional trailhead, mentioned in all the older trail guides, watch for the blue "Entering Rattlesnake Lake Recreational Area" sign on the right side of the road just before you see the lake; take the unpaved road on the left. Some of the guides say to drive up to where the road turns--sorry, there is a gate here now, but you can see the turn just a little way further on. Park on the side of the road, being careful not to block the gate.

For the official Cedar Falls trailhead to the John Wayne Pioneer Trail (Iron Horse State Park) enter the recreational area, keep to the left (passing the dinky parking lot for the Rattlesnake Ledges trailhead), and watch for the sign. You won't miss it. (By the way, Washington State Parks has dropped the daily use fee.) You can also park in the Rattlesnake Lake parking lot across the road, but do be careful to get back before the gate is locked.

By the way, there's a nice view of Cedar Butte from I-90 east bound as you descend the long grade to the main North Bend exit. It's that low, nearly conical peak that the highway is pointed right at.