High-frequency ferrite ceramics exhibiting high permeability and low magnetic loss have been recently attracting more and more attention owing to the rapid development of modern communication technologies. It is known that the magnetic performance of ferrites is strongly associated with the morphology of their polycrystalline structure. In this work, we focus on the control of grain growth and densification process for planar Co-Ti doped M-type barium hexaferrites, BaCoxTixFe12-xO19, by one-step sintering (OSS) and two-step sintering (TSS) techniques. Experimental results indicate that a uniform and fine-grained microstructure is achieved by the TSS method. More importantly, the ferrites prepared by TSS demonstrate high permeability (mu' = 18-20), low magnetic loss (tan delta(m) = 0.1-0.3), and high Snoek's product (>25 GHz) in the frequency range of 100-400 MHz. By fitting experimental data, we have determined that low magnetic loss is derived from the small damping coefficient of spin rotation in terms of Kittel's theory. Therefore, the TSS technique provides an effective and efficient approach to prepare planar BaM hexaferrite materials for ultra-high frequency (UHF) communication devices requiring low loss and high Snoek's product.