In the mornings what you do is drive up to the slug line and shout "Crystal City", depending on whether the line you are going to will have one or more destinations. If it is a CC only line then obviously it's implied and you don't have to shout. Typically drivers will ask the slugs where they're heading when they reach the ramp at Army/Navy drive as it's customary that you drop the slugs off at their destinations and not at the slug line in the mornings. Usually you can drop slugs off at intersections or the closest you can get them to where they want to go.

To get to CC from HOV yes you would take the Pentagon exit, and turn right at the ramp and go from there.

In the afternoons just drive up to the slug line and either shout your destination or make a sign and show it to the slugs. If you're heading to 610 or 17 the line is at the uppermost area, near the actual white slug sign at the curve. The Woodbridge area lines are next to them on the sides. Drivers tend to form two groups of lines there depending on space. There's always slugs/drivers in the afternoons, just depends on whether you get more of one type or another, it's hard to tell. Anytime between 3:30-5:30 is good, and if you really get stranded you can always swing to the Pentagon and pick up there. Good luck.