As others have indicated, there is no such thing as a, "foolproof strategy to win at chess." If there were, we'd all be using it. :)
But there are things you can do to help, if you're willing to spend some time learning. See if your library has a book like "Pandolfini's Ultimate Guide to Chess," "How to be a Winner at Chess," or, "Starting Out: 1 e4!: A Reliable Repertoire for the Improving Player" - but if you get the last, get only the last... There's a whole series of "Starting Out" books by Everyman Chess. That's the one you probably want. But be careful: All beginning players tend to study openings to excess, which is actually detrimental because you really need to learn endgames first, then tactics, then positional strategy, and only then (when you know what a winning ending looks like and have the tools to get there,) should you want to learn the openings which will lead to middlegames which lead into the endings you can win with.
Second: Play! Play online, very short games (like 5-10 minutes per side.) You *will* lose a lot. Plan on it. But the purpose of doing this is to get you used to the things that can happen over the chessboard in general. Bonus points for figuring out from lots of those games just why you're losing. Do you not see your pieces are under attack? Does your opponents use combinations of two or three moves that end up losing a piece? Do you put your pieces in places where they can be taken for free? Noticing what happens during your play and experimenting to prevent it will improve your play.
Third: Learn how to record your games using chess notation. I'd recommend my own pedantic tutorial on it, but I recently lost all my blog images- oh, well. Try http://main.uschess.org/docs/forms/KeepingScore_2007.pdf to start out. Aside from the intimidation factor ("Look, brother! I'm writing down all the moves of our games.... :O"), when you play over the games again you will start noticing where your mistakes are occurring.
Finally: Find a local chess club. If you're in the US, use the locator at http://main.uschess.org/component/option,com_wrapper/Itemid,198/ to find a club near you. Chess clubs often have either people who give lessons for money and/or other players who will look over your recorded games with you to help you learn.
Now, you may not want to do any of these, or just a few of them. But if you do them, you will definitely improve your play. Work consistently at it, and you will beat your brother. And have a lot of fun learning and playing in the meantime. There are no shortcuts, only degrees of how much you're willing to learn and how quickly you learn it in.
Good luck!