An answer responds to each allegation in a complaint and raises any defenses to it. It's often treated as a formality, but a rushed or generic answer can waive defenses that would otherwise have been available later in the case.
Respond to each allegation specifically
Most rules require admitting, denying, or stating a lack of sufficient information for each numbered paragraph in the complaint. A blanket denial of everything, without engaging paragraph by paragraph, is often improper and can be struck.
Affirmative defenses have to be raised — or they're gone
Defenses like statute of limitations, failure to state a claim, or contributory negligence generally have to be affirmatively pled in the answer. Leaving one out can mean losing the right to raise it later, even if it's a strong defense.
Counterclaims belong in the same filing
If the defendant has their own claims against the plaintiff arising from the same situation, most rules require raising them as counterclaims in the same answer rather than in a separate later filing.
Don't miss the deadline
The window to answer after being served is typically short and strictly enforced — missing it risks a default judgment, regardless of how strong the underlying defenses might have been.