Some people also have a custom to give some charity in the merit that the person should be well.

If you know the person's Hebrew name then you can say certain verses from Psalm 119.  (Psalm 119 consists of groups of 8 verses, each group dedicated to one letter of the Alpha Bet; the first eight verses begin with the letter Aleph, the next eight begin with the letter Beit etc)   We say those verses  that begin with the letters of his/her name, then the verses that begin with the Hebrew letters Kuf, Reish, Ayin, Sin, Tet, Nun. Those letters spell out the phrase in Hebrew that means that the evil decree should be annulled.

You can also have the Rabbi of the local Synagogue say a prayer for him when they read the Torah.