You can do it by fertility magic but you need to do it prior to the birth of your target so it is a bit limited, (naturally you'd first have to reinvent fertility magic based on the few scattered fragments of information that remain).
Another demonstration of Rego Filum!
There are also a few existing ways to get the Gift or something like it (homunculi, Odin's Sacrifice, or asking a demon and signing on the dotted line) and one way to give it to your children (Petrus Virilis' kids all receive the Gift automatically, hence him being bred like a stud animal).
Integrating Fertility Magic, of course, allows for the reliable production of apprentices and would lead to a significant shift in the culture of the Order - though unless you're a magus Mercere, it's usually less trouble to find an apprentice than to make one, so I'm not sure it would drastically increase the number of magi or anything. It'd mostly lead to a major challenge to the Oath regarding surrendering one's apprentice to Bonisagus, since there would suddenly be a lot of magi with an interest in changing that rule.
Can you get the gift by breaking in to the garden of Eden and eating from the tree of knowledge? Or do I miss-remember?
Yeah, that too, if you don't mind being stuck in animal form for the rest of your life.
The common thread between all methods of gaining the Gift in life is that they're difficult, carry a high price or usually both. You know, story fodder.
The Fertility Ritual of AM p.54ff Fertility Magic does not initiate the Gift.
Cheers
Another option is to get converted into a magical being and then acquire the gift as a quality. Though it seems like a bit of a backwards way to go about it...
I'm wary of that choice for a game. If you can be a gifted magical creature,then you open up the option of immortal mages with few drawbacks by becoming low might magical creatures rather than using the immortality initiations that we have. That doesn't seem like as much fun to me.
It is RAW in ROP:magic
of course the order as a whole hasn't decided that might based magi can be members. And if you can't be a member you better not know parma magica. So you my have some hard choices...
RAW in the sense that the rules describe magical creatures, there are examples of people becoming magical creatures, and nothing in the text says "you can't do this".
This doesn't mean that it is a good idea. I choose the language;"wary" and "doesn't seem like as much fun to me" with full understanding that there is a path through the rules that can lead to this destination.
There are in fact rules for transforming people into magical beings, and rules for magical beings to gain new qualities, so it's a little more laid out than simply not being forbidden... although these rules being in different books and nobody having been hit over the head with it it probably wasn't something anyone realized was in the RAW.
From what I understand of the attitude towards RoP:M here on the forums, it's generally considered a "GM's cookbook for developing interesting NPC's", rather than a "PC's guide for cool stuff for my character to do". It seems to work very well for the former, whereby the GM uses it as a general framework for narrative balance. It doesn't work so hot for the latter, and is apparently even more prone to abuse than many other books.
It is indeed known for many years, that the RoP:M Qualities and Inferiorities are verrry easy to abuse, unless closely moderated by SG or troupe.
Cheers
That said, transforming the Gift seems like it would be within the capabilities of the Magic Realm and adventuring in the same. Of course, it does require at least three seasons of adventuring in a highly dangerous world - without yourself being Gifted - before you could unlock the Gift. That's a minimum - it might take more than thirty pawns of vis at troupe discretion, and it might not work at all - though if it doesn't work, it should definitely provide breadcrumbs toward a method that can grant you the Gift.
Hi,
This, mostly.
The rules work ok for creating GM NPCs. They work terribly for creating PCs. The badness is both hidden by and caused by the presentation, from which it is easy to infer that reasonable results are likely just by setting a number of points and then buying stuff.
Like, I'll happily use RoP:M rules if they are allowed in a game. But many of the RoP:M rules are broken (in the sense that they don't do what they say they do) and are unnecessarily cumbersome. Naturally, it is one of my favorite supplements. 
/2 But I'm all too aware that these rules don't play nicely with other AM rules.
Since these are the rules we have, some suggestions:
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Just because a Quality exists doesn't mean it can be taken. Feel free to ban anything you don't absolutely like. Just because something can be validly expressed using the rules doesn't make it valid.
1a) Only allow Transformed Human or Gifted to be acquired during play, with unanimous troupe agreement. Generally, you die when you get bitten by a radioactive spider. Feel free to make exceptions, but you deserve what you get.
1b) Beware of Variable Power.
1c) Do not allow Immunity to might strippers. Especially if the character has taken Reduced Might.
1d) Feel free to flatly ban any character with Reduced Might. The queasiness you feel on encountering such character sheets is completely normal. -
Handwave anything about the magic realm, tethers, extracting vis. On the positive side, we now have rules for this stuff. On the negative side, we have these rules. Much of the 'fluff' is interesting, but the rules are heavyweight, awkward, involved, baroque and counterintuitive.
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Except for elementals, do not use the Awakened Item rules. Instead, treat such an item as something with an active spirit attached, and use the spirit rules. This way, you can bind the spirit of a tower or a mountain without having to deal with the size of the thing, or trying to express its Soak (and getting very different results from the ordinary version), etc. Take a Flaw (perhaps similar to the Soqotran patrons) to express being bound to something. The results will make a lot more sense.
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The Magic Animal section needs a rewrite. In a point-based systems, identical stats should result in identical point costs, but this is not true. Try creating a magical squirrel with the same stats as a magical bear to see what I mean. But the problems don't really break the game so I wouldn't worry. Note that not all magical animals follow the rules for ideal animals.
Other stuff, but this is a good start. Unless, of course, I'm a player in your game, in which case my characters should get to ignore all of this terrible, terrible advice.
Anyway,
Ken