Wherever 10 Jews live together, everyone must pitch in to build or rent a designated building to daaven in at all daavening times. (MB 1,2)
The shul should not be built by idolaters, but for them to fix the roof is fine. (BeH “livnos”)
If the shul is large enough for everyone and all get along with one another, it is forbidden for some people to break away to form their own shul. If their hearts are separate and they have attempted to bridge their gap but did not succeed to cease arguing, it is better to form a separate shul. (MB 2)
Besides for a shul, everyone must pitch in to purchase a library including sifray Torah, Neviim and Kesuvim. Talmud and its commentaries should also be purchased so youngsters and elders alike can learn. If there are books available to borrow elsewhere in the city then this obligation is reduced only to buying a sefer Torah. (ShA1 – MB 3)
A shul should be built upon the highest elevation of the city. This does not apply if, anyways there are buildings of gentiles which are built so high that you won’t be able to notice that the shul is high. Try, anyhow, whenever possible. (ShA 2 – MB 5)
You are allowed to daaven in a shul that has an inhabited upper storey above it. Just make sure that they keep the quarters clean. (Rama 2)
When building next to a shul window, keep an 8 amah distance. (ShA 4 – MB 9)
Do not pour dirty water in a public place that people may walk by and slip. (MB 9)
The aron should stand in the direction that people are facing when daavening Shemoneh Esray i.e. towards Jerusalem. If, for some reason, it isn’t possible and the aron was built in a different direction – there is an unresolved doubt as to which direction people should face when daavening. (ShA 5 – MB 11 – BeH “shehu”)
Plan that the entrance to the shul to be opposite the aron so people will bow towards the aron upon entering. (ShA 5)
The bima must stand in the center of the shul so everyone will be able to hear the baal koray. (Rama 5)
Don’t make more than 6 steps up to the bima. (MB 12)
The chazzan should come down from the bima to in front of the Aron and face it for Shemoneh Esray just like everyone else. (MB 13)
The elders should sit to the side of the aron and face the congregation. The congregation should sit in rows facing the aron and the elders. The elders shouldn’t sit facing the bima with their backs to the Aron. (Rama 5 – MB 14)
Rabbonim are allowed to darshen with their backs to the Aron Kodesh. This is because the sefer Torah is in a separate domain, and it is only temporary. (ShaH 13)