Coordinate ideas are connected by coordinate connectives. The most popular coordinate connectives on the GMAT are and, but, or, and nor. Knowing these will help you to find sentences that have a faulty parallel structure problem.

Make sure that you express parallel ideas with the same grammatical form, whether they are all verbals, phrases, or clauses.

There seems to be faulty parallelism in the last thing the boy does...

Right after the boy got out of bed he ran out of his room, jumped down the stairs, and then the boy was eating breakfast.

Eating is a gerund which doesn't match the form that was used for the 2 other activites the boy did after getting out of bed. To correct the sentence you must make the last part of the sentence parallel.

Right after the boy got out of bed he ran out of his room, jumped down the stairs, and then ate breakfast.

The two most popular ways to compare ideas are the following...

... as ... as ...

(this) [more/less] ________ than (that).

To play basketball is as much fun as swimming.

Either change To play into Playing or change swimming into to swim in order to fix this sentence.

Dancing is more fun than to play video games.

Dancing is more fun than to play video games.

Either change Dancing into To dance or change to play into playing in order to fix this sentence.