～て

A verb's て-form on its own is a casual request: 〜～てください with ください left off. You say it to friends, family and children.

For "don't", the same goes for ないでください: the ない-form plus で.

Who you can say it to

Without ください the request is direct, and it is only for people you speak to in the plain form. To a teacher, a boss or a stranger, keep ください, or ask with 〜～ていただけますか.

• × 先生、ちょっと待って → 先生、ちょっと待ってください

Softer and firmer

How it lands depends on the voice and on what you add. ね makes it friendly; よ presses the point and can sound impatient. Said flatly, the bare form is close to an order.

To make it a question rather than an instruction, add くれる: てつだって手伝ってくれるきごう？ is "will you help me?", and てつだって手伝ってくれないきごう？ is softer still.