1. They Barely Fill Out Their Profile
A person's life and personality may be quickly and easily shared with the world via the internet. It's your choice whether or not you want to share information about your interests. If this person you are dating doesn't fill in his or her own information, you need to be alert. Either this person doesn't have any hobbies or interests at all, or he/she tries to hide the genuine intention. If so, you have no reason to continue to communicate with him/her online.
2. They Use Vulgar Chat-up Lines
If you receive uncomfortable and aggressive information from the opposite sex on the Internet, you will feel very uncomfortable. The way a person talks to you will show how they will treat you in the future. If they comment on your body in a sexual way, please stay away from them. But if they ask you what kind of cute dog is in the picture? You can keep talking with them. You may receive some tacky chat-up lines, some may be cute and charming, while others may be vulgar and derogatory. Please be sure to distinguish them.
3. They Are Controlling
It's always a good idea to try online dating before agreeing to meet this person. If someone comes up strong, or puts pressure on you to meet before you're ready, pump the brakes if you need to and set some boundaries. If they don't respect these boundaries, they don't respect you. In addition, if someone immediately gives you a list of all the things they want in their future partner, this may be some red flags for controlling behavior.