Age: 15
Profession: Student, going into grade 10

1. According to the rules of punctuation:
Sometimes

2. According to the sense of your text:
Often

3. According to the intonation and the rhythm of your text :
Sometimes

4. According to the “signal words” (for example, conjunctions) in your text:
Often

5. According to your own intuition:
Always

6. Write down your own variant:

Often

I personally think that correct punctuation is whatever gets the idea you want to portray to your audience, which for me at least, doesn't often conform to the rules. Fortunately, my English teacher likes me so I can get away with it

Hope I helped