Long "i" in American English

I've been wondering about this thing for a while. when I say words with the "long i" sound in them, such as I, lie, tie, my, fine, and so on, I know I'm dealing with a diphthong. I'm talking about the sound aɪ (using Ipa). I'm just not sure which simple sound I should use for the onset of this diphtong. Should I start with an Open back unrounded (ɑ using Ipa) or should I use an Open front unrounded (a using Ipa).
I'm interested in the most common way of pronouncing it in the U.S.. I won't say "General American English" because I know there's no such thing.. but at least the most common, and the least weird way of saying it (the one that wouldn't sound foreign)
Thank you

I'm from the northern USA myself and my onset is open back unrounded. That's how it's generally spoken around here, I believe.

Another distinction for a lot of people is between the 'long i' before a voiced consonant (or no consonant) and before an unvoiced consonant:

rye /rai/
ride /raid/
right /rəit/

The actual onset may vary, but I don't hear 'right' pronounced with the same open onset as in 'ride'.

"Another distinction for a lot of people is between the 'long i' before a voiced consonant (or no consonant) and before an unvoiced consonant:"

Isn't this known as Canadian raising?

I would disagree: for American English, the onset that you should use is a central [a]. A back [ɑ] would be characteristic of a strong New York accent (and, more prominently, of London, Estuary and Australian accents), and would sound out of place in General American or even here in New England. The phenomenon that guest2 notes is known as Canadian Raising, and is quite common in the northern half of the United States, but it's not necessary that you use it as a learner of General American.

I myself have a phonemic split for "long 'i'" between what can be written as /ae̯/ and /əe̯/; unlike the typical case of Canadian Raising, this is not truly allophonic anymore (for reasons I will not discuss here). As for their actual realizations, /ae̯/ has an actual low *front* starting point and a mid or high-mid front ending point and /əe̯/ has a mid central starting point and a mid or high-mid ending point. And yes, /əe̯/ is much more central-to-front rather than low-to-high in articulation, and thus is not articulated very much at all like the typical instance of /aɪ̯/ in North American English.

You just can't learn to pronounce that way.

-A back [ɑ] would be characteristic of a strong New York accent -

Yup. Think Fran Drescher.

Lazar: "I would disagree: for American English, the onset that you should use is a central [a]. A back [ɑ] would be characteristic of a strong New York accent (and, more prominently, of London, Estuary and Australian accents), and would sound out of place in General American or even here in New England. "

I agree. For my own part, I haven't heard an open-back unrounded "ai" in quite some time outside of a NYC dialect.

I wonder how common true front-onset /aɪ̯/ or its equivalent (like that here) is in NAE dialects as a whole myself...

So, let me get this straight.. The onset should be a central [a].. so not a Open front unrounded, but more central, right? I'm want to be sure because I'm italian, and I guess my italian "a" is in the front.. but I don't think I should use that italian sound when I say "my", "try", "lie", when I try to sound General American. It just doesn't sound right.
So, a little back than the italian "a", but not as far back as the ɑ ?
I know this post might sound silly, but I'm trying to nail the right sounds
Thanks for your help

Old speech-and-diction textbooks used to suggest that the speaker open his mouth widely while relaxing his tongue in order to make the first sound in "ai"; however this results in an un-American "ai".

American speech has evolved a bit since then. Nowadays, you'd need to raise your tongue just a little bit, in the middle, to approximate a raised American AI sound.