Edward Cook has a good summary and analysis of the Qeiyafa Ostracon on his blog. He concludes that the inscription is:
(1) A text written from left-to-right. (2) A text written in the Old Canaanite form of the alphabet, the form that the letters took before (but more about this later) the evolution of national scripts. (3) A text whose language, although North-West Semitic, is still undetermined. (4) The most significant fact about the ostracon, in my view, is the date. If the dating of the level it was found in is correct – late 11th/early 10th century BCE – then the use of this Old Canaanite script is surprising. Within a century or less of the ostracon’s writing, another inscription would be made in ancient Israel of a very different sort.
Read the whole thing for his explanations.