1) If something seems off with the person you begin dating, you're right. Walk away. The chances are you aren't missing out on Mr. or Mrs. right so don't worry about it. It's so much easier shutting things down early.
2) The person you date will more than likely be putting their best foot forward, just like you, so the fact is, you don't completely know this person until you've spent quality time together. Saying you just met the person of your dreams, isn't a realistic statement.
3) Since both parties are somewhat hiding their faults, a good way to figure out who the person your dating is, is to checkout their friends. Are they kind and nice or superficial and selfish? Do they have somewhat stable lives or are they all over the place? The thing is that the person you date probably isn't the odd person out in the group he or she hangs out with. Not that this is always the case but we all tend to attract that which we are.
4) Does the person seem to live within their means or are they hanging on by a thread because of bad financial decisions? If the person drives a BMW and has a waiter/waitressing job, it's probably good insight into the person's spending habits regarding wants and needs. Has the person been able to live successfully outside of their parent's home?
5) Is the person steadily employed? Does the person have an idea of a career path?
6) Do you have some important common interests that will get you out and doing things together?
7) Are you both similar in your religious beliefs?
8) Is the person good with animals, children, and your family and friends?
9) Is the person fine with you continuing spending time with friends. Not that they should be going out partying on the town all the time, but if the person you're dating tries to separate you from family and friends and make you feel guilty if you don't spend time with him or her, it's a dangerous sign. Controlling relationships never turn out well.
10) If many of your family and friends don't like the person and you think you're in love with him, listen to them and not your heart. In almost all cases, women wish they would've listened to the warnings from other people. When you're in love the blinders are on, it's human nature. You're in a fog and your decision making ability is flawed. The bottom line is trust other people they can save you a lot of heartache.
There are no guarantees in life. You won't find the perfect woman or man because if they were perfect, they wouldn't be with you. :) If you use some of the ideas above, you'll have a better chance of finding the right person for you.