How Do You Know When You Are In Love Or In Lust?

You will need to think of the person and care for the person without the thought of the appearance of the person in mind. And even then (without thinking of the appearance or the sex appeal of the person if you can still feel and get emotional about him/her then its love).
And on the contrary, if you happen to get intimate with someone and from there on only that becomes the prime reason for you to think about him/her then its just lust.

The only way to find this out is to embark on a long term relationship with the person. After a few months when the initial ardour has cooled a bit you will start to realise whether or not you want to be with this person for ever. You can still be in love with someone without an active sexual relationship at all. Lust goes, love doesn't!

When your inlove you will know. When they are on your mind constantly and no matter how long you've ben with them your feelings are still bran new and you never get tired of them. You want to hold them every second of everyday and they are the first thing that pops into your mind when you  wake up. And if anything ever happend to them you would be terribly hurt like you've lost a family member. All you want to do is make them happy and spend every day for them and make sure their life is complete. And the best part is,they will feel the exact same way. ;)

When your in love your partners happiness is more important than your own.

When you are in love you cannot be happy and you cannot sleep properly.