what we typically use in our laboratory is to preserve the brain in a solution of paraformaldehyde at 4% for 24h at 4ºC. Some publications recommend a shorter period (4-6h), which should be enough to maintain the structure without altering too much molecular structures. Afterwards, you should dehydrate the sample in a solution at 30% sucrose, at 4ºC for 24h-48h. Then, completely dry the sample and keep it at -80ºC. This sample will be useful to be cut in a cryostat (optimal cutting temperature for brain: -20ºC).
Other option will be formalin-fixed and paraffin embedding.
Your question needs more elaboration. Variations in technique happens according to the need for specific methodology. In addition to Teresa GB's answer I just want to add 30% sucrose solution (for over night) for better sectioning results.