For the young, the ba’alei tshuvah, and the uninitiated or uneducated,
Lu’ach Eretz Yisrael was first published by Harav Yechiel Michel Tikochinsky in 1905 in Yerushalayim for the “yishuv hayashan”, when Rav Shmuel Salant zt”l was Rabba shel Yerushalayim IH”K.This is minhag haprushim talmidei haGra, and has been accepted since day one as the only authority for minhagei eretz yisrael. It has all the minhagim and dinim of the year, including the davening, times of the molad, krias hatorah and haftorah, olos hashachar, netz tables and more.
Do we say bameh madlikin? Till when can we eat chametz? When is bi’ur ma’asrot? Do we say ka keli? Do we say lamenatzeach? Do we say tachanun? Can I get a haircut erev pesach? Does this village keep 14 or 15 Adar for Purim? When does the chazan take the sefer torah during rosh chodesh bentching? Where should I put my menorah on Chanukah? It’s all in there.
The lu’ach is sold in Elul at all seforim stores or straight from the Tikuchinsky family. It is the only lu’ach accepted by all, mostly because it is the only lu’ach at all. (The rabbanut also has a lu’ach, but it is Rabbanut oriented, Zionist, has minhagei hasefaradim,and is not comprehensive, r”l. No one in the ashkenazic yeshivishe world uses it)
Needless to say, not all sects keep all the same minhagim, timetables or psakim, but those differences are the exception and not the rule. Those who know, also know when their private or community’s minhag deviates from the lu’ach and they act accordingly.
A few years ago, a chutz la’aretz version was published and is available in America.
In summary, in Israel, when there is a question in shul,whether in Meah She’arim, Bet Shemesh, Telzstone or Kiryat Sefer,(or even Tel Aviv) the answer is always “Do what the lu’ach says”.
The lu’ach says to say Sholom Aleichem on the seder night.