Use a free e-mail account dedicated to your online dating site. If you already use a free e-mail account in your day-to-day life, you should make a new one. The reason for this is because e-mail addresses are often the first pieces of information people find about you on online dating sites. If you use your usual one, people may be able to search it and find things like your real name, your phone number and even your address. You would not give this information to a stranger on the subway, so do not give it to a stranger on the Internet either.
Choose a dating site you need to pay for. Free dating sites attract more people, as they do not have to invest as much into making an account. They may even attract more unscrupulous people for the same reason. So, if you are serious about online dating you want to be around similarly-serious people, and should therefore join a site you need to pay for.
If someone messages you and asks to meet immediately, say no. Rather, you should message back and forth, then think about talking via an instant messenger, then talk on the phone and then have a meeting. Online dating is not like real-world dating where you can meet in person sooner. Since you have no access to these people other than what they say about themselves you need to take it slow and wait to meet them in person.
Once you do decide to meet someone in person you need to do it in public. This is for the same reason that you had a gradual progression--you only have as much information about them as they have provided you, and you need to be careful. So, meet in a cafe, restaurant or other place with a lot of people around you. This will both keep you safe and ensure that the other person is actually interested. If they are willing to meet you in public now, they actually want to get to know you. If they would rather meet in private then this may not be the case.