* Make sure that your complaint letter is short. There is absolutely no reason for your complaint to be longer than one page. The shorter your letter is, the quicker it will get the attention of the manager that you expect to help you. Some employees right out their entire work history with the company and how wonderful they have been during their career before getting to the point. A five-page memoir about your work issues is likely to be put on the bottom of the pile of documents of your supervisor or hr manager and not get the attention it needs promptly.
* Make sure that your complaint letter uses proper terms. You must use the words "discrimination" and "harassment" in your complaint. Otherwise, the employer will later argue that they didn't know that you were subjected to these unlawful acts. Some employees use just about every other term in their complaint, including "disrespectful," "unfair," "lack of dignity," "humiliating" but this is often not enough to put the employer on legal notice of unlawful conduct at workplace. Disrespectful and unfair can mean many things. Thus, you should be more specific.
* Make sure that your allegations are specific. Using the terms harassment and discrimination is essential but that alone is not enough. You must not limit your complaint to generic adjectives such as "abusive," "inappropriate", "hostile" as these terms could mean many things. Instead, quote specific words that you believe to be discriminatory and describe specific actions that you consider to be harassment or discrimination. In other words, stating in your complaint that your manager called you a "fucking nigger" is much more effective than stating that your boss was very rude to you and used a racial slur. Likewise, stating in your complaint that your boss told you that he would love to fuck you over his conference room desk is much better than saying that your boss has propositioned to you at work.
* Consider not making your complaint anonymous. Although there are some advantages to making an anonymous complaint, especially if the victim of discrimination or harassment is someone other than you, when you are trying to protect yourself, consider to actually sign your name on the complaint. This way, the employer who tries to retaliate against you for complaining will have a much harder time arguing that they couldn't have retaliated against you because they didn't know that you were the one complaining.
Keep the above tips in mind when complaining about discrimination harassment and feel free to use this sample letter complaint for discrimination / harassment at workplace.