Griffons can be a excellent race for newbies. However, playing something so different from the run-of-the-mill does have its pitfalls. So I'd to offer some suggestions to help new players know what a "typical" griffon is like. Though of course, the only official limits are in the help files.
Descriptions
1) Stick to the classic half-eagle, half-lion divided somewhere behind the shoulder. Despite the help files, being part hawk or part tiger gets negative reactions from a lot of players. Tailfeathers and leonine front paws also get negative reactions. You've leeway to use rare colors, such as black. However, blatantly unnatural colors like bright green should be avoided.
2) "Help size" reveals that a griffon should be about nine feet long. By custom, they're a tad larger, typically 5 feet at the shoulder (which translates as about 10 feet long for a big cat.) There's leeway here, but you should normally avoid making yours over 6 feet at the shoulder, which is getting into a giant's weight class, or making them only 3 feet at the shoulder like lions.
Roleplay
1) Griffons take bonuses to intelligence as well as physical attributes. They should not normally be played as dumb brutes with bad grammar. Avian accents are welcome, but certainly not necessary.
2) Body motions should match a griffon's peculiar anatomy. For example, instead of using the smile social, use an emote that conveys the idea: "chirps brightly", "eyes sparkle as his beak gaps wide", whatever. Or maybe even an inscrutable emote, since griffon expressions are supposed to be hard for humanoids to read: "clicks his beak".
3) Griffons can range from the feral to the civilized, though IMO the best griffons have some qualities of both. But do remember that per the help files, they are "altruistic", a very strong word.
4) For your backstory, don't worry about picking a birthplace with griffon NPCs. The great majority of families are simply fabricated, off in the mountains of their particular country. Being a bit vague about exactly where they are is downright common.
Being raised by humanoids or having escaped from the Empire are acceptable stories, but perhaps a bit overused.