1. A sentence with 1 verb: Put the adverb of frequency before the verb.
Tom never flies. He always takes the bus.
2. A sentence with more than 1 verb: Put the adverb of frequency before the main verb.
They have often visited Europe. We didn't ever do our homework.
3. A sentence with 'to be': put the adverb of frequency behind the form of 'to be':
He is always late to class. My friend was never out of bed early.