Is there an anti-discrimination and/or anti-harassment policy?
If there is not an anti-discrimination and/or anti-harassment policy in the handbook or the an existing policy is vague, ambiguous, or ineffective, then you might be able to find relief due to the faulty handbook language.
Does the handbook talk about "Probationary Periods"?
Most employers who have "probationary periods" will tell you that the probationary period is a time for evaluation during which the employee may be fired for any reason. In Wisconsin, however, AN EMPLOYEE CAN BE FIRED FOR ANY REASON ANYWAY (unless there is a contract for a definite period of time or unless the termination was based on a discriminatory or possibly another illegal motive). Some employees have argued with success that, if they were terminated after the probationary period, the termination had to be for "just cause" or "good cause" and that the employee was no longer "at-will."
Does the handbook state a system for progressive discipline?
If the handbook states a system for progressive discipline (like, the first offensive is a verbal warning; the second offense is a written warning; and the third offense allows for a suspension or termination...), then the employee has an argument that (s)he was not an at-will employee and the employer may have been required to follow the steps (depending on the language of the handbook) of discipline prior to termination.
Does the employer consistently apply the handbook's policies?
If the employer does not consistently apply the handbook's policies (or any other employment policy) or applies is to some people and not others, then the employer may have a breach of contract type of claim against the employer for a termination, for example.
Does the handbook say that it is not a contract?
If the employer wants the employee to be an at-will employee, the handbook will say (1) this handbook does not constitute a contract between the employer and employee; and/or (2) the employee is an at-will employee. If the handbook does not say this, the employee might have an argument that (s)he is a contract employee and not an at-will employee.
Did the employer include non-compete or other provisions restricting future employment in the handbook?
If the employer included restrictive provisions like non-compete, non-solicitation, and confidentiality provisions, but did not give the employee money or some other "consideration" in addition to continued employment, then those provisions might not be valid or enforceable. (As with everything, however, including every part of this legal guide, each situation differs based on each situation.) And by the way, if the handbook say it is not a contract on one hand, but on another hand it attempts to bind the employee to a restriction on employment (like a non-compete), then the handbook is contradicting itself, which means that it is subject to interpretation. See Step 7, below.
Does the handbook use language that is subject to interpretation?
If the handbook uses words or phrases that are subject to different interpretations by different people (such as "just cause"; "reasonable"; "appropriate notice"; "industry standards"; community standards"; etc.), then there is an argument that the handbook's language is vague or ambiguous. When a document like a contract or an employee handbook is deemed ambiguous, then it is construed against the drafter (the employer), which is usually to the employee's advantage.