In short, your sentences need to be balanced.
Railroad tracks, fence posts, and gymnastics bars. What do all these things have in common? You got it: they're parallel.
Got a series of nouns, verbs, or adjectives? They need to be structured the same way. Ditto for clauses or items being compared and contrasted. If two of your three items are fragments, the third better also be a fragment. If you start two bullet points with adjectives, each bullet point needs to start with an adjective.
Just like breakfast.
"The beauty pageant finalists' talents included singing, tap dancing, and reciting all of the lyrics to Billy Joel's "We Didn't Start the Fire.""
Wow. That is a lot of lyrics. This sentence keeps it parallel because all of the verbs in the list are –ing verbs (a.k.a. gerunds).
"Carlito's Italian Street Meats is the hottest restaurant in town, so it's better to make a reservation than to show up demanding a table."
We hear their bratwurst parmigiana is to die for. Here, the sentence is parallel because the two options being compared are both infinitive phrases (to+verb).
"After discovering that their son had thrown a party while they were away, Todd's parents were most concerned with the giant hole in the ceiling and with the whereabouts of their beloved cocker spaniel, Sporty."
We're pretty sure those two concerns are unrelated. At least we hope they are. Regardless, they're both prepositional phrases, so this sentence is balanced and parallel.