This study reports the effect of various reaction variables of a tailor-made sol–gel synthesis method on the morphology and photocatalytic behaviour of nanostructured anatase TiO$_2$ photocatalysts. Reaction variables like solvent effects, hydrothermal and microwave conditions, type of capping agents and calcination affect the TiO$_2$ crystal growth, and thereby, their optimal conditions are anticipated and discussed in detail. It is proposed that TiO$_2$ exposed with characteristic facets can be prepared by a hydrothermal-modified sol–gel method employing a quaternary solution system at pH 3 along with cetyltrimethylammonium bromide (CTAB) as the capping agent. The optimal hydrothermal temperature affected the restructuring and crystallization of TiO$_2$ by enhancing the phase transformation from amorphous to anatase. TiO$_2$ crystal growth under microwave assistance was faster, which primarily resulted in low-energy facets exposure. The primary determination of photocatalytic efficiency of the samples was obtained from the photodegradation profiles of model dye methylene blue. An interesting find was that TiO$_2$ synthesized under hydrothermal treatment in the presence of CTAB had a morphology determining behaviour at pH 3 favouring the selective stabilization of co-exposing high energy {010}/{100}, {001} and low energy {101} facets in TiO$_2$. The optimum percentage of high- and low-energy facets resulted in superior photocatalytic activity due to the spatial separation of photogenerated charge carriers. Furthermore, the present study has a great perspective on how particularly the reaction variables determine the direction of crystal growth of nano TiO2 and thereby its morphology that directly affect its photocatalytic efficiency.