Select a stone for the job that is oval shaped and large enough for your message or design. Select a hard variety of stone (no sandstone or fieldstone) that you can polish. Test if the stone is hard enough by scraping its surface with a knife. If grains of sand break off, it is too soft.
Wash the stone with warm water and soap to remove any loose debris. Set it aside to dry.
Sand one side of the stone down using 60 grit sandpaper until it is flat and can hang against the wall. The stone will have severe scratches all over its surface, but that is okay.
Dip your stone into water. While it is still wet, sand down the large scratches using 140 grit sandpaper. The finer grit will help buff out some of the larger scratches, but some will remain.
Drill an oval shaped hole large enough to fit the head of a nail into the back of the stone. The hole only needs to be a quarter of an inch deep in order to work. This hole will catch the head of a nail you insert into the wall in order to hang the stone.
Sand the surface with 400 grit sandpaper once you have sanded out the largest of the scratches. This sandpaper is so fine it will do more to polish the stone than shape it, so ensure you have the shape you desire before you switch to this sandpaper.
Clean the remaining grit from the face of the stone. Sketch the words of your message onto the face of the rock using a pencil. Keep the markings light so that you won't see them through the paint.
Brush over the sketched letters using a fine paintbrush dipped in acrylic paint. Allow your personal handwriting style to reflect in the painting to give the stone a more personalized feel. Allow the paint to dry.
Wipe off the face of the stone using a sturdy cloth covered in powder polish. Do not scrub so hard that you rub off the painted words, though.
Run a stud detector along the wall where you will hang the stone. Mark the studs with a pencil. The weight of the stone makes anchoring it to a stud necessary, so choose which stud you will use.
Hammer a nail directly into the stud. Leave the head of the nail sticking out a quarter of an inch so that it can catch on the back of the stone.
Place the back of the stone against the protruding head of the nail. Move the stone along the wall until the nail catches the indentation you drilled. Shift the stone around until it hangs straight.