Jaabir Ibn 'Adbullaah (radhi-yAllaahu 'anhu) related that the Messenger of Allaah (sal-Allaahu 'alayhe wa sallam) said: Verily, the best supplication is:

الْحَمْدُ لِلَّهِ

All praise is for Allaah.

Alhamdu lillaah.

...and indeed, the best form of remembrance is:

لاَ إِلَهَ إِلاَّ اللَّهُ

None has the right to be worshipped except Allaah.

Laa'ilaaha'illallaah.

At-Tirmizi 5/462, Ibn Majah 2/1249, Al-Hakim