The results of our investigations show that on an untreated flat substrate, the discotic liquid crystals align side-on (or homeotropically) if the sample is slowly cooled from the isotropic phase. If the sample is kept in the glassy or crystalline state for several hours, the alignment inevitably changes to edge-on, (planar or heterogeneously planar) in this phase. However, if the sample is heated from the glassy/crystalline phase, the alignment alters slowly from edge-on to side-on. This anchoring transition is dependent on the temperature and the substrate. On the other hand if the flat surfaces are treated with a polymer the alignment achieved on cooling is also mostly side-on. A grooved surface or slightly uneven surface promotes the edge-on alignment (homogeneous and even heterogeneous). This type of alignment persists even when the surface is treated with a polymer. The side-on alignment once achieved is found to be thermodynamically stable in the discotic phase, where as the edge-on alignment has the lower energy in the glassy/crystalline phase. A plausible explanation is given.