do you mean to force someone to fall in love or to strengthen it?
you can check the spell books but its always more effective to just do some research and right your own. find candles and incense that are associated with love, maybe some rocks then right your own, it can be hard work but not always.
i don't suggest using a love spell that forces or influences against their will for someone to fall in love with you because this can generate loads of bad karma. but if your trying to strengthen love between you and a partner its a great way to do it:) just make sure they know about it first!