Generally, the rule is that if there is a verb form with -ed, American English will use it, and if there is a form with -t, British English uses it. However, these forms do not exist for every verb and there is variation.
The British use of "t" at the end of words reminds me of German because they have plenty of verbs that use a "t" at the end. Which makes sense, because old English is scarily similar to German.
The list I found is a part of a List of American vs. British Spelling, where there's lots of good stuff, including Common Words in American and British English, and related links.