Scenarios should follow the Given-When-Then structure. This makes it clear to the reader what the scenario is doing and what the expected outcome is.

You should not have Then steps before When steps, or When steps before Given steps, and you should not have Given steps after When steps.

Bad

Feature: logging in

  Scenario: logging in
    Given I have visited the website
    Then I log in with "username" and 'password'
    When I will see my account

Good

Feature: logging in

  Scenario: logging in
    Given I have visited the website
    When I log in with "username" and "password"
    Then I will see my account