First you must identify the leak; for example, look for automatic withdrawls on things you no longer use (For us it was Blockbuster. They were taking money out each month regardless of the amount of movies we rented, but I realized we were only watching 1 or 2 movies a month, so I cancelled them).
After you identify the leak, plug it up!
Another leak for many of us is change, didn't realize those annoying shinny coins were leaks did you? As a way to plug up the leak I take the change that is dumped from my husband's pockets and whatever is in my wallet and every few days I put it in our change jar.
Over the last 3 months we've accumulated $40 in change alone. Every 6 months, I'll go deposit it to our savings account! I plugged up a leak and it's now more money in our account!