Casting a successful spell involves much more than finding some spell on the internet or in a book, saying some words, lighting a candle, waving a wand of any of that sort of thing. In order for magic to work you need to understand how and why it works in the first place. Grounding and centering, visualization, focus and intent, energy manipulation, etc are all necessary first steps to even begin to have a chance at a spell actually working...and more importantly to prevent a spell from back-firing on you.
So, my advice for anyone who is truly serious is to start by reading a few books and practicing the exercises those books will give you. Once you have mastered the basics you won't need anyone to give you spells, you'll be able to create your own spells that will be far more effective than anything you find on the net. Here's the books I suggest:
"Before You Cast a Spell" by Carl McColman
"Spells and How They Work" by Janet and Stewart Farrar
"The Veil's Edge" by Willow Polson
"Modern Magick" by Donald Michael Kraig