Lets start with the obvious, Never under any circumstance give out personal information. Listen to the conversation, are they really interested in getting to know about you, or getting to know where you live and what your last name is? Phone numbers and address should only be given with complete confidence. If you feel that the conversation is headed in that direction, become suspicious. Don't worry about making quick judgments.
Wait before you meet someone in person. Have several long conversations over the phone and chat first. A person's tone of voice can really be a clue. Make sure that you are also making the calls and you know how to get in touch with the person. Avoid cell phones, land lines are always much safer, smarter and can be tracked. It is better to be safe than sorry.
Choose the place where you first meet carefully. Make sure that it is a public place with many people. Stay away from things like alcohol that can impair your judgment and always get the drink directly from the bartender. Stay away from situations where you two are left alone such as cars or apartments. Meet up somewhere and don't be picked up from your house.
Financial information of any kind to a dating sites partner should never be given out. Don't even talk about salaries or wages and definitely not bank information. There is absolutely no reason as to why they would request or need this information. Even after a year, predators are blessed with patience.
Listen to whether they talk about money. These people can be tricky. Sob stories are the first hint that they are in it for something else. Never give money to people you have met through dating sites. If you hear a lot of stories about debts, sick mothers, hungry children, etc, most likely they want more then a relationship out of you.
Strange obsessions about certain topics can also be a dangerous sign. If you notice the person talking obsessively about things like children, don't let that slide. Take it seriously and again, even if you are wrong, end the connection. Topics could be any obsessive talk about one thing. Instinct is a key to making good decisions, if it feels weird, it is weird.