The process took time, and was earned the hard way. Here's a look through ten years of SG-1, and the interactions between Bra'tac and Daniel.
Bloodlines. Bra'tac is delightfully impressive in this first meeting, but he isn't very impressed with the Tau'ri. He swipes at Jack, sneers at Sam, and, as mentioned above, grabs Daniel by the wrist and threatens to snap it. He seems incredulous that these puny humans could possibly have killed Ra and angered Apophis... and won Teal'c's loyalty.
Here are some screencaps of that moment. (Click on thumbnails for full-size picture.)
Bra'tac certainly does open his mouth and then gnash his teeth right next to Daniel's hand, but that might have been emphasis. I really don't think he was trying to pretend to bite (I mean, really), especially since he specifically says, "I could snap you like kindling!" But to each their own interpretation.
[ETA: Thank you, morjana, for pointing out below that yes, Tony Amendola confirmed in an interview that Bra'tac really did threaten to bite Daniel. :) The link to the interview is here, and here's the pertinent excerpt:
Bra'tac has some great improvised moments such as the "bald" gesture that accompanies "Hammond of Texas", and the moment when Bra'tac meets Daniel and bites him:Now back to your regularly scheduled meta. ;)]
I have no idea where that came from except the director. Part of Bra'tac is loosely based on what they gave me, but the guy who directed the first episode I was in was a guy named Mario Azzopardi...he was a big Maltese man and everything was big.
Acting is very schizophrenic because you'll have one director who'll say "no, smaller, smaller, you're doing far too much, you're doing far too much, smaller," and then you'll have a director [saying] "what are you doing? You know, give me something" and Mario's larger than life, and I have to make that adjustment...I'm watching him and he's a bear of a man, much bigger than I am, so I said "this take I'm going for it. I'm going for it. I don't care, what are they gonna do? If they don't like it, they'll cut it."
That's the one where, you know, you puny humans...(mimes biting Daniel's hand). So it was really spontaneous. It was one of my completely unscripted...that's an example too. They could have said "woah, wait, wait, we didn't write...you're biting him? We never wrote that!" and Michael didn't flinch, he played it within the [character]...I had just met him maybe three hours earlier!
Jack slowly earns Bra'tac's respect by his actions and his beliefs ("I serve the SGC under a General Hammond... Just a man. A very good, very bald man, from Texas."), although Bra'tac will still call him "human" for some time to come. Sam and Daniel, however, manage to impress Bra'tac (and Drey'auc) with their complete disregard for protocol:
"You dared steal from the sepulcher of the temple?"
"It is sacrilege!"
Sam and Daniel look at him blankly - obviously without comprehension of the concept that they should fear to rush in where Goa'uld feet dare to tread. Daniel hands the thermos with Junior-to-be to Bra'tac, and a little respect begins to grow.
The Serpent's Lair. We next meet Bra'tac on Apophis' ship, when he has worked his way into Klorel's good graces for the express purpose of joining the attack on Earth in order to sabotage it. He is annoyed that SG-1's presence has destroyed his plan to pit Klorel against Apophis, and that the "shuttles" that Daniel and Jack mention don't have much firepower to offer. He leads them to the peltak and is almost killed in his attempts to create a diversion. Daniel is left behind to "watch their backs" and is fatally wounded. Bra'tac doesn't even react to the news that Daniel is "staying behind" - perhaps because he, too, has lost his followers, and sees Daniel's death as all of a piece - and joins the rest of SG-1 in transporting over to Apophis' hatak.
Interestingly, Hammond thanks Bra'tac and has him escorted from the Gate room before the revelation of Daniel's presence. He isn't surprised to see him the next time they meet, though, so one assumes that Teal'c told him about Daniel's survival - and it isn't a stretch to suggest that Bra'tac would be impressed that Daniel not only managed to survive, but made it to safety.
Family. By now, Bra'tac already treats the human members of SG-1 with respect - he's still calling Jack names, but there's a definite element of affection, too. Daniel gets called "Doctor Jackson," and Bra'tac agrees with the advice that Daniel gives Teal'c.
Maternal Instinct. Here is where we really see the level of trust between Bra'tac and Daniel. Teal'c brings Bra'tac to Daniel to discuss Apophis' slaughter of the Jaffa on Chulak, and together, they realize that Apophis is searching for the Harcesis child. They discuss Jaffa legends and literally connect the dots to find the one planet in a sector of space that fits the legend, but isn't on the Abydos cartouche - Kheb.
Bra'tac joins Daniel in the temple, and, unlike Jack, follows Daniel's lead in doing as the monk asks. Although he does not yet accept what we will later discover is Ascension - he still has, as he tells Teal'c, "false gods to slay" - it is clear that he reveres Kheb, and what it represents.
Then comes that climactic scene, when the monk lies dead (proof that Oma Desala is not all-powerful?) and a barefoot, weaponless Daniel begs them to put down their weapons:
"Jack, if you're ever going to trust me on anything, now is the time."
Who is the first to listen, and to urge Jack to follow suit?
After this, Daniel and Bra'tac are mostly together in a team setting, where they work with mutual respect and accord. So I'll just mention a few highlights:
Threshold. Bra'tac insists on performing the Rite of Mal Shorran on Teal'c. "Trust in me," he says, "all of you."
Daniel answers, "Whatever you need."
Orpheus. While Bra'tac may or may not know of Daniel's role in Changeling (Teal'c did not include it in the report, although he might have told Bra'tac - who certainly believes in Ascension - privately), he joins Teal'c and Hammond in giving Daniel credit for his and Ry'ac's rescue from Erebus.
Threads. Bra'tac's grin, on seeing Daniel alive, is bigger than anyone else's in the room.
Stronghold. Bra'tac and Daniel as Lois and Clark! Okay, that's my old fandom roots showing. :) But there is something delightful at seeing Bra'tac and Daniel working together as an investigative team to discover what happened to Teal'c, and their final exchange - when Bra'tac announces the vote for democracy, and Daniel congratulates him - is truly moving.
Talion. Daniel sits vigil over Bra'tac and is there when he regains consciousness. Bra'tac tells Daniel all he knows about Arkad, and Daniel acts as Bra'tac's spokesman at the meeting with Arkad and Landry.
In conclusion: Daniel was always predisposed to respect Bra'tac as the man who mentored Teal'c and inspired him to rebellion, but liking would have come as a surprise. And Bra'tac had to overcome his prejudices not only against humans, but against non-warriors. The friendship and mutual respect between these two is an unexpected pleasure, and I'm very glad the series gave us their friendship to enjoy.