There are various approaches, but the most common route to this cache starts at the Mount Margaret trailhead, up a forest road from exit 54 of I-90. Note that a Northwest Forest Pass is required to park at the trailhead.
From there, the hike is 2 miles one way with 1,600 feet of elevation gain. Follow the Mount Margaret Trail until you are about 300 feet from the cache, at which point you'll need to bushwhack up to the cache location.
This is a moderate mountain hike, so good shoes, water, and other hiking essentials are recommended. Don't forget your camera - weather permitting, you'll have nice views of Mount Rainier and the Snoqualmie Pass area. (And go the short distance from the cache to the ridge top, where you'll have truly spectactular views.)
This area of the Cascades can have snow well into the summer (often into July), so plan your trip accordingly. Your chances of finding the cache if it's under snow are almost zero, and simply finding the location without the cache does not qualify as a find.
The container is a small lock&lock, similar in size to the original cache placed in June 2000 by ajroman and his girlfriend Karen (who famously found their container - a recipe box - at a yard sale for 10 cents); credit goes to GrnXnham for the current box. There's a spoiler photo in case you need it.
While you're here, you really should get Mount Margaret and Livin' on the Edge. Both offer breath-taking viewpoints over the area (but are not recommended for acrophobes).
If you use a Garmin or DeLorme GPSr, Northwest Trails could prove helpful.
Page views added Oct. 4, 2012. This cache was placed in June 2000, so this counter doesn't begin to capture all the visitors to this page, but it's still fun to see: