Make character design sheets. It will help you flesh your characters out more and keep track of details about them. Sometimes creating the sheet helps you spawn even more ideas for backstory as well, and you can incorporate that into your stories.
if it's been a minute since you wrote your last chapter, reread it before working on the new one. it'll help you maintain the vibe.
find songs that suit the vibe of your story well, and play them while writing a specific scene to help you channel that emotion.
daydream constantly from your character's pov. If you hear about a random situation or even a very common one, think how your characters would respond to that situation. it helps you solidify personalities, and sometimes you can include those scenes in your stories too (for instance, i was watching a video about women's pregnancy cravings and imagined what my MC would be like if she was pregnant, and how her husband would respond to her asking him to bring her her pregnancy craving at an unholy hour.)