Your best chance to weed out scammers and liars when online dating is when you are still online, before you agree to that first date. When messaging back and forth, make sure it is the type of conversation you want to have.
Messaging is a good way to communicate that keeps a record. If you think someone is changing their story, you can always go back and look. As the relationship progresses online, you may find people owning up to little lies that told you in the beginning, which is a good sign. If someone owns up to little lies, they might not be hiding anything.
Bigger lies you may only find out when you meet them in person, when they can no longer hide their weight or baldness. Confront them in a gentle way and judge the reaction. If someone gets angry and defensive then maybe that isn’t the only thing they have lied about and its best to leave now. If they lied and are underage, leave immediately and let them know from your computer that you will not date them. Trust your gut.
Online dating can be fun and a little daunting. Pay attention to the details people tell you, if there are consistently inconsistencies, bring it up before you agree to meet. You are in control here, don’t settle for a liar in the beginning and expect changes later.