Would it be adverb then verb or verb then adverb?

There are basically 4 positions:

before the subject - Occasionally Jon missed the bus.

after the auxiliary or be verb - Jon is occasionally late for the bus. Jon has occasionally missed the bus.

before the main verb - Jon occasionally missed the bus.

end of the clause - Jon missed the bus occasionally.

It depends on the type of adverb where they go. Some such as occasionally (above) can go in all positions.