A clear or cohesive first-contact policy is never eludicated. From the events around the Raloi, and Yahg though, we can infer a few things. Both of these races were recently contacted by the Citadel races. Contact with the Krogan, though they were a pre-spaceflight species at the time, was done with a specific goal during wartime, and can't serve as an accurate example.
Notes on the Yahg
- The Yahg were roughly equivalent to current day humans. They have the
beginnings of a space program.
- The citadel races initated contact, and sent a delegation to meet with the Yahg. We do not know if one race led this delegation or not.
Notes on the Raloi
- The Raloi had just launched their first space telescope, placing their tech level around 20th century Earth.
- They initiated contact with the Asari. Or alternatively, the Asari responded to being noticed by the Raloi.
- First contact was completed on the Raloi planet, after which the Raloi were invited to visit the Citadel.
In addition to these two events, there is mention of First-Contact Procedures in the events around the re-discovery of the Manswell Expedition.
Believing it very possible that the colonists had no knowledge of the rest of the galaxy, the Alliance decided to proceed using first contact protocols. Rather than send in a full military force, they sent in a team of military experts, medics, sociologists, anthropologists, linguists, psychologists, geneticists, and other experts to a facilitate a dialogue with the colonists.
It is unclear if these protocols are Human-specific, or enforced by the Citadel. They do appear to be compatible with what we know of the Raloi and Yahg contacts.
There are some things we can determing or infer. It does appear that there are standard first-contact protocols, but they only appear to pertain to pre-spaceflight, or at least pre-relay species. Notably, the Turian's responded to discovery of Humans by occupying their colony, rather than attempting a traditional diplomatic contact after the battle at Relay 314. The humans were already settling worlds and using the relays at this point, so they were treated like a newly-discovered galactic power.
The Citadel Council appears to openly contact new races, but only if they are at the point of reaching space. Before the altercation with the Manswell colony, the Asari were observing a pre-spaceflight race, with no mention of contacting them.
Standard protocol, at least for the Council and Humans, is to send a wide delegation to the new race, meeting them on their planet. If the initial contact goes well, then a delegation of the aliens is brought to the Citadel for culture and legal education.
We do not know if technological uplift or Council recognition is provided automatically, or if it must be requested/earned.