How do you earn prestige points in MW3?

Question

How do you earn prestige points/tokens in Call of Duty Modern Warfare 3?

Is it only from leveling up to 50? Is there any other way?

Answer 1

You receive one prestige token per time you rank up to level 80 (not 50) and then prestige.

You can also get prestige tokens for other Call of Duty games that you've prestiged in, with one token per game being awarded to you.

Source

Answer 2

See Prestige transferring from Modern Warfare 1 & 2? - for each previous game you've prestiged in, you get an additional prestige token.

So you can get four tokens from the previous games, and ten tokens (one per prestige) from MW3.