Strong verbs are an important part of German II grammar. The following websites have lists of the most common strong verbs. You don’t need to memorize these lists, but they can provide a very useful resource when writing in the Perfekt.
About German has a great strong verb list, in addition to having hundreds of other pages about German grammar and culture.
This strong verb list includes which helping verb to use, the first and fourth columns are the ones you’ll want to focus your attention on.
This third and last list is a PDF ready to be printed out and kept with you at all times!