Typically, you should start with the root chakra and work your way up to the crown chakra. Think about it like growing a plant. Without strong roots, it is hard for the rest of the plant to be healthy. That being said, after you work your way up through your chakras, you might discover that it becomes easier to go back and clear previous blockages that still feel "stuck" in any specific chakra. Also, sometimes the voice of intuition might tell you just to work on a particular chakra. That is totally fine to do.