Hi All,
this is the method that I used to stain Osteoblasts
Section should be cut at 10um wide. (usualy for best results frozen section are prefered)

We measured alkaline phosphatase (ALP) by the azo-dye
coupling method.
We used Freshly prepared incubation medium
consisted of 25 mg of alfa-naphthyl phosphate disodium salt
(Sigma, St Louis, Missouri) and 25 mg of Fast Violet B salt
(Sigma) in 25 ml of 0.05M Tris-HC1 buffer (pH 10.5)
containing 0.025M MgC12.
Sections were incubated for
seven minutes at 37°C, rinsed in reaction buffer, postfixed
for 15 minutes in aqueous 10% paraformaldehyde and
mounted with glycerol-gelatin (Sigma).
For any other question email me.
Guy

You can use counter staining (Hematoxiline, Methyl green)