Time is usually placed at the end of a sentence.
EXAMPLE: I visited the Eiffel Tower in 1999.
Time may also be placed at the start of a sentence.
EXAMPLE: In 1999, I visited the Eiffel Tower.
Place comes before time in all cases.
EXAMPLE: I visited the Eiffel Tower in Paris in 1999. I visited the Eiffel Tower in 1999 in Paris. (INCORRECT)
An adverb (in bold) is usually placed between the subject and the verb.
EXAMPLE: He often looks at the sky. EXAMPLE: She always grumbles about the weather. EXAMPLE: Tom seldom talks to anyone.
Some adverbs can be used at the beginning or end of a sentence.
EXAMPLE: Normally I go to the library with her. EXAMPLE: Sometimes I feel tired for nothing.