Recently, there has been a spelling reform of the German language. The following are a few points that have changed:
1. Write ss after a short vowel, and ß after a long vowel or diphthong. Please note that ß is not used in Switzerland or Liechtenstein and a lot of people don't pay attention to this rule anyway. Also, there is no capital letter that corresponds to the lower case ß, so it must be written as SS.
2. Words that are now capitalized: (auf) Deutsch, Mittag, Abend, Morgen, Recht haben, Leid tun…
3. The forms of Du (familiar you) are no longer capitalized in letters.
4. A comma is not necessary when two independent clauses are joined by und.