Why are they called Zifim?
R. Yochanan (Sotah 48b): They are people who are Mezayef (falsify) their words. 1
R. Elazar (Sotah 48b): They are people from Zif - "Zif va' Telem u'V'alos" (Yehoshua 15:24).
Maharsha (48b): They said "we will hand him over to the king" (verse 20), and they were not able to do so. Torah ha'Temimah - they said "David is hiding with us", i.e. he thinks that we are with him. Later, David realized that they are liars, and they told Sha'ul (26:1) "David is hiding in Giv'as ha'Chachilah." He did not hide with them, rather, also from them.
When did the Zifim tell Sha'ul?
Radak: This was before. Verse 15 said that David saw that Sha'ul is pursuing him, for he heard from Zifim!
Why was Sha'ul in Giv'ah?
Malbim: Sha'ul had returned to Giv'ah and ceased to pursue David.
What is "ba'Metzados"?
