It already said above (25:1) that Shmuel died!
Rashi: This explains why he asked from a Ba'alas Ov. If Shmuel were alive, he would have asked Shmuel. 1
Radak citing Koheles Rabah 7:4: Above it says so for the disgrace of Naval. Everyone else was eulogizing and mourning Shmuel, and he made a feast!
Malbim: (a) This explains why Sha'ul needed to remove Ba'alos Ov. When Shmuel was alive, people would ask him or other prophets, and not the dead! When Shmuel died, Nevu'ah ceased also from other prophets. (b) Now Pelishtim gathered for war. In his lifetime they feared his power, even though David was with the Pelishtim. (c) Now Sha'ul feared. Until now, he trusted in the merit of Shmuel.
I.e. do not say that he wanted to speak to Shmuel only because Shmuel was dead, and knew what Shamayim had decreed. (PF)
Why does it say that they buried him in Ramah and in his city?
Rashi based on Targum Yonasan: "In his city" refers to "they eulogized him"; they eulogized him, a man in his city. Radak - all those who came to bury him eulogized him in Ramah. Those who did not come, each eulogized him in his city. This was a reward for going around to all cities to judge Yisrael.
Radak #1: There were two Ramos - "Min ha'Ramasayim" (1:1). They buried him in the one in which he lived.
Radak #2: They buried him in the city, and not outside it.
Malbim: This hints that when he died, also his influence departed; Nevu'ah ceased also from other prophets.
Why does it say that Shmuel removed the Ovos and Yid'onim from the land?
Rashi: Therefore he needed to search to find a Ba'alas Ov.
Radak: This shows that if Shmuel were alive, surely he would not have sought a Ba'alas Ov!
What are Ov and Yid'oni?
Sanhedrin 65b #1: Ov is one who speaks between his joints and between his elbows. Yid'oni is one who puts a bone of a Yadu'a (a certain Chayah) in his mouth. Radak (24) - [both of them] tell the future. 'Between his joints' means that he makes a low noise come from between his joints and his underarm through [the Ba'al Ov's] actions; he bangs his arms. 1
Radak (24) citing Sanhedrin 65a #2: He offers incense to a demon, and the demon answers and talks.
Sanhedrin 65b #3: He raises [the Mes] on his Ever, or he asks from a skull. Radak (24) - the former makes it seem that he raises the Mes [on his penis], and makes its voice heard from under the ground, from the opening of its grave, like Sha'ul heard Shmuel's voice. The voice is very low, like it says "v'Hayah k'Ov me'Eretz Kolech" (Yeshayah 29:4). The latter has a skull of Shoham (a precious) stone or crystal, 2 and he does actions until it seems that a very low voice comes out, and it seems to ask and answer.
Refer to 28:14:3:1-3, 6.
Radak citing Ramban (Hilchos Avodah Zarah 6:1): He holds a myrtle branch and waves it after offering incense, and the asker thinks that someone speaks to him and answers him from under the ground in a very low voice, as if his ear does not hear, only in his thoughts. Lechem Mishneh - the Ramban wrote in Perush ha'Mishnah that what he 'hears' is hallucination.
Radak citing Ramban: He takes a skull of a Mes and offers incense to it, until it seems that a very low voice comes out from under his underarm and answers him.
