Since the dead cannot praise God (Ps. 88:10-12; 115:17), the psalmist calls on God to save him so that he may praise Him among the living.
Gates.
In contrast with the “gates of death” (v. 13), these gates are at the city entrance, where the assembled people exchanged news (ancient substitute for a daily newspaper). It was a convenient place for publicity (the agora of the Greeks, the forum of the Romans).
Daughter of Zion.
The inhabitants of Jerusalem; Zion, or Jerusalem, being regarded as the mother city. The occurrence of the name “Zion” here and in v. 11 above indicates that that psalm must have been composed after Zion, or Jerusalem, became the capital of the kingdom and the seat of worship.