Make your intentions about what you are looking for in a man. Do you want to just date, do you want a relationship, or something more? Make your boundaries known to the men you are communicating with. Many men on online dating sites at first seem very nice, intelligent, and charming. But, there is a high percentage of men that do want only a strings free relationship (intimate ecounters only). Some also engage in sexual conversations early on when talking to them via IM, telephone, or e-mail. Do post current photos of yourself that show your whole body and not just your face (make sure the photos are clear and not blurry). And do read the men's profiles carefully before you send a message to them or whatever the method of communicating is on the site you are on.
When you have spoken to the men for a while not just a couple of days and decide that you are comfortable meeting the man choose a neutral location. And drive yourself to the location and don't accept a ride from him no matter what. Depending on what you are looking for in a man be cautious if he only talks about sexual matters or makes the first date out to be a financial arrangement. If you are going for a coffee or drink on the first date and he is interested in you it shouldn't be a financial hardship for the man to treat you to a coffee or a drink. If you have to pay then this is a warning sign. For the first date keep the topics of conversation neutral and ask questions to get to know him better. See if what he has been telling you are truthful. And also tell a friend that you are meeting someone from online for a date so you have someone to talk to, to depcompress what occured on the date to see if there truly was a connection or not. And let the man follow up with a call, e-mail, or IM to show interest in you for another date. If he doesn't keep up the frequency of communication you are use to while you were communicating online before you met in person, he is either busy or isn't interested in you.
Sorry to sound harsh and cynical I just want you to be safe and be warned.