First, you find the simple subject and simple predicate. If the '-ing' form of the verb is not part of the simple predicate, then determine how it is used in the sentence. If it's in a noun position, then it's a gerund. If it is used as an adjective, then it will be a participle.
A gerund is an entity made from a verb by integrating "-ing." Gerunds function as entities. Thus, gerunds will be subjects, subject complements, direct objects, indirect objects, and objects of prepositions.
