Hunter Walk, formerly of Google and Linden Labs, has an excellent primer on how not to congratulate people over Twitter.
He describes three different (yet pesky) ways that people toss around accolades in 140 characters or less.
There’s the “suck up congrats,” in which you tweet some sort of empty sentiment at a public figure who will almost certainly never see it.
You’ve got the “humblebrag congrats,” where you recognise someone and still manage to make it all about yourself.
And then there’s the “undeserved congrats.” This one’s pretty self-explanatory. Just praise the people or companies that deserve it.
For some specific examples, head over to Walk’s blog.