[verb] + …
Don't + [verb] + …
Let's + [verb] + …
The imperative starts with the verb in its base form. There's no subject, and the form is the same for one person or many.
For a negative, put don't before the verb.
Be works the same way.
Instructions, recipes, directions and signs use the imperative.
With friends and family, and in instructions, the imperative is normal. Please makes it softer. When you ask someone you don't know for something, a question is more polite.
Let's + verb is a suggestion for you and the other person together. The negative is let's not.
Always and never can start an imperative.