The haben / sein choice: some fine points (for beginners who enjoy detail)
 

• With about five verbs the haben/sein choice varies regionally. Sitzen, stehen, and liegen are conjugated with sein in the South, even though the rules would call for haben. Anfangen and beginnen are conjugated with sein in the North, even though the rules would call for haben. The conjugation with haben, which the rules predict, is considered standard for all these.

 

• The verbs that may not be explained by the three questions are verbs meaning "to happen," "to succeed," and "to fail," which take sein. However, it might be argued that these involve a sort of change of condition.

 

• Many grammar books indicate that a distinction can be made with a number of verbs of motion, such as schwimmen, between sentences in which the activity is done simply for exercise or recreation, in which case haben is used, and sentences in which the activity is done to reach a destination, in which case sein is used. Thus, you might say "Ich habe heute geschwommen," on the one hand, and "Ich bin nach Philadelphia geschwommen," on the other hand. However, this sort of distinction does not seem to be made very often at all by actual German speakers, who usually just use sein with all these. The distinction may be, and probably should be, ignored by even advanced learners.