Understand what a declarative sentence is. Most sentences are declarative types. Declarative sentences offer a statement that doesn't requires the reader or listener to take any action. They are simply informative sentences such as "That necklace is pretty" or "You are very kind."
Learn what an interrogative sentence is. This type of sentence asks a question, such as "Are you cold?" or "Where were you?" Interrogative sentences always end with a question mark.
Understand what imperative sentences are. Imperative sentences give orders or directions. An example of an imperative sentence is "Put your coat away" or "Hurry!" These sentences require actions from the reader or listener and end with either a period or an exclamation point.
Learn about exclamatory sentences. These sentences are always used to make exclamations and often end with an exclamation point. "You look great!" is an example of an exclamatory sentence.
Read the sentence. After understanding the other three types, it should be easier to figure out what type of sentence it is. If you have a sentence you are wondering about and can rule out the other three, the sentence must be a declarative sentence.
Look at the punctuation. A declarative sentence must end with a period; however, exclamatory and imperative sentences might also end with periods.
Look for a command or an action. If after reading the sentence you are inclined to perform some type of action, it is not a declarative sentence. Sometimes the sentence type changes simply by adding a word or different punctuation. For example, the sentence "You need help" is a declarative sentence because it is making a statement. By changing it slightly to "Do you need help?" you are changing the sentence type to a question, therefore it becomes an interrogative sentence.