Go to Route 111, go to the sandstorm, and go all the way to the right. There you will find two fossils--the Claw Fossil and the Root Fossil. Pick one, then go to Rustboro City. Go to the president's office and go in a room with lots of scientists. Talk to the one in the lower right hand corner. Then go outside and walk around for about 30 seconds and go back in to talk to the same scientist as before. He will give you your Pokemon from the fossil.
This is me probably sounding nit-picky, but... I'm pretty sure you don't have to walk around at all... Just leave the building, and go back in again...
I drop by every now and then... I shall never be just a memory! *cackles*
... Not back to the regularly scheduled thread... ^^;
hmmm did you know that in the sand storms that if you click on some rocks they give you items for exaple soft sand or pokeballs sometimes even ultra balls