The best solution would be to [not welcome salams *at all*](http://meta.islam.stackexchange.com/a/107/22):

> I strongly encourage anyone reading this to abstain from adding unnecessary salutations to their questions and answers. This isn't a discussion board, answers are not replies, and if the majority of each question's excerpt quoted on the front page of the site is the same then you've thrown away what should have been an eye-catching introduction to your question...

That said, in the more general case of people using the "wrong" transliteration for Arabic terms (which is hardly limited to greetings), you have to remember the fact that the only "right" way to say "Assalaamu 'Alaikum" is "السلام عليكم‎‎" (other examples at "http://islam.stackexchange.com/q/11171/22" and "http://islam.stackexchange.com/q/23709/22")

We generally prefer to keep a [loose standard of transliteration](http://meta.islam.stackexchange.com/q/3/22) for consistency, but if the only *problem* with a question is that they're transliterating it *differently* (note: "differently" is not the same as "wrongly") then editing the post to fix *only that* is probably just a waste of time (aka noise), as is arguing with them to use a "better" transliteration.

And if you *are* going to correct someone's transliteration, [don't just stop there](http://meta.islam.stackexchange.com/a/1796/22): Fix as many problems in the post as you can (and in my experience, there's almost *always* more than the one).