あまり + [verb]ない あまり + [verb]ません
あまり + [i-adj 〜い → 〜く] + ない あまり + [i-adj 〜い → 〜く] + ありません
あまり + [na-adj] + ではない / じゃない あまり + [na-adj] + ではありません / じゃありません
あまり + [noun] + ではない / じゃない あまり + [noun] + ではありません / じゃありません
あんまり is a casual spoken variant of あまり
あまり~ない is used to express that something is "not very," "not much," or "not really" the case. It softens a negative statement, indicating that something occurs to a limited degree or that a quality is not strongly present. あまり always pairs with a negative form – this is a key rule to remember.
Place あまり before the verb in its negative form to express that an action doesn't happen much or often.
Place あまり before the i-adjective in its negative form to express that something is not very [adjective].
Place あまり before the na-adjective followed by じゃない or ではない.
In casual spoken Japanese, あまり is often pronounced あんまり. The meaning is the same, but あんまり sounds more colloquial.
A common mistake is using あまり with an affirmative form. Unlike English "not very," the negative must always be present in the Japanese sentence. You cannot say ×あまり食べる – it must be あまり食べない.