At the heart of any German sentence is the conjugated verb. Usually there is another component to the sentence - the subject in the nominative. Many verbs require an object as well. The majority of German verbs require an accusative (direct) object, e.g. "nehmen" (to take) and "treffen" (to meet).

Examples:
Ich nehme den Füller.
Ich möchte dich treffen.

Some verbs can have another (indirect) object in the dative. Verbs that express the acts of giving, receiving and telling fit into this category.

The nominative subject ("ich") indicates who is carrying out the action.
"Helen" is the dative (indirect) object of the action.
"den Brief" is the accusative - or direct - object of the action.

In sentences with two objects, usually the dative object comes first, followed by the accusative object. So a typical main clause with the subject placed first would look like this:

More:

Generally, the dative object also precedes the accusative object when sentences are formulated as questions or imperatives. Only the subject and verb switch positions:

However, if the accusative object is a pronoun, then it moves in front of the dative object, even if the dative object is a pronoun, too.

Ich schicke Helen den Brief.
Ich schicke ihr den Brief.

Ich schicke Helen den Brief.
Ich schicke ihn Helen.

Ich schicke Helen den Brief.
Ich schicke ihn ihr.