Si quieres ver al dentista, es importante que tú conciertes una cita previamente.If you want to see a dentist, it's important that you book an appointment in advance.
El decano siempre está ocupado. Es importante que tú conciertes una cita previamente.The dean is always busy. It's important that you arrange a meeting in advance.
Es importante que tú conciertes una cita previamente. Aún así, es difícil que todos asistan.It's important that you schedule a meeting in advance. Even then, it will be hard to get everyone to attend.