It's well past time for a good claying! There are many clay bars out there and most of them will do the job. I use the Clay Magic bar and you can get the kit at your local auto parts store or wal-mart for about $10. Dwayne carries the big Clay Magic bar at premiumautocare (link at the bottom of the page). If you go with another brand (Mothers, Meguiars) it's probably best to choose the fine grade versus the medium (medium is generally for heavy overspray).
Wash your vehicle. Tear off a small piece (1/4 or 1/5) of the bar and flatten it out (I like sort of an oval shape). Lube the surface with the solution in the kit and move the clay back and forth to pick up debri. Some folks like to go back and forth on the top panels (hood, roof, truck) and up/down on the side panels. You can also use a quick detail spray or really really soapy water as a lubricant for the clay.
Two keys to claying:
1. Use plenty of lube so the clay does not grab the surface. It should easily glide along the surface.
2. Once the clay is dirty, fold the dirty side together and make a new oval at that point. Don't just flip the clay over. You'll get more use out of the piece by folding.
Your suface will be nice an clean at this point. Now, I recommend a good polishing and then waxing from this point, but that is another thread....