Prepositions (voorzetsels) express the relationship between the phrase group of which the preposition is a part and a word in the sentence. A preposition is almost always a noun. An example of a preposition in a sentence is: Hij zit voor het huis. This chart shows examples of almost all prepositions.
There are various tricks to recognize a preposition. The first trick is to put … de kast behind the word. For example: op de kast, voor de kast, bij de kast. 
The second trick is to put … het feest behind the word. For example: op het feest, tijdens het feest, via het feest. 
Use this exercise to test what you just learned.