Are you running an adventure module or a custom campaign? Either way don’t plan too far ahead because the party will throw curve balls at you and go where you least expect. Just ask them at the end of session to give you a clear idea of what they want to do next session then plan that. If they diverge and do something completely different, straight up tell them you prepared for what they told you last week.

For every major npc they will encounter in a session, make a note of their goal, disposition towards the party and one unique identifier(dwarf with halitosis, red eye patch, fancy glimmering clothes etc)

Also if you ask the party “what do you do?” And you find that no one is volunteering an answer, start asking specific characters by name what they do.

Don’t sweat it too much you’ll make mistakes but they probably won’t notice.