The best practice is for a kehilla to spend money on scrolls of n’viim which have been written according to the laws of sefer Torah and Megilla for the Krias Haftara. This spending is more important than beautifying the shul. (MB 1 – ShaH 4)
The Mogen Avraham says that if you read Haftara from a printed book, it should at least contain the entire Navi. If you do not have one (or the one available has been printed by heretics), you may be maykil to read the Haftara that is printed in the Chumash. (MB 1 – ShaH 1)
Haftara was instituted to be read only b’tzibbur and only after Krias Hatorah. If someone left the minyan before Haftara leaving less than 10 men, do not do Haftara. However, if someone left after beginning the Haftara, you should finish it even without a minyan. (ShA 1 – BeH “rak”)
You need to listen and have in mind all of the 21 blessings being said by the olim l’Torah and the Haftara and answer “omayn” after them. This will help compensate for some of the 100 berachos that are missing on Shabbos. (ShA 3)
Because of this, the olim must bless out loud for all to hear. (MB 5)
Do not answer omayn if it isn’t the end of a beracha. For example: after “…hane’emarim be’emmes…” and after “…emmes votzedek…” . (MB 5)
If you called up someone for Maftir and you realized that he does not know how to read the Haftara, it’s okay bedieved. Someone else can say the Haftara and it’s berachos. If the Maftir can at least read the words by repeating them word for word after someone, he should do so. But l’chatchila, call up for Maftir only someone who can also read Haftara with the berachos. (Rama 4 – MB 7)
If the Haftara will be read from klaff by a baal koray, then you can call up for Maftir someone who will only say the berachos. The baal koray will be motzi everyone just like by Krias Hatorah. (MB 8)
If the Haftara is read from a Navi, just listen without reading along. If the Haftara is read from a Chumash it is proper l’chatchila to read along in a whisper. (MB 11)
Do not begin the Haftara until g’lila is finished (and the sefer Torah is covered). This is because everyone is obligated to be attentive to the Haftara like they are to the parsha of the sefer Torah. (ShA 6 – MB 12)
When you finish the Haftara, do not remove the Haftara text from the table until after the berachos are recited. (MB 12)
The deceased neshamos need kapara. Therefore there is a minhag to mention them in public on Shabbos so all the living listeners can take mussar. (BeH “v’nohagu”)
There is a minhag to bless those involved in the welfare of the tzibbur. Also, to recite Yakum Purkan and Av Horachamim (sometimes). Ashray should be last – as to not interrupt between Ashray and Kaddish (which is said because of the pesukim of Ashray). Y’hallu is not considered an interruption. (Rama 7 – MB 15)