Deliver newspapers every morning if there's a route in your community. Find out if there are routes available in your area by contacting your local newspaper. Collect your bag of papers each morning and ride your bike from house to house to hand them out or have your parents drive you around. Most newspapers have to be delivered very early around 5 a.m. so be prepared to wake up at the crack of dawn.
Check with your local bank to see if they're giving away cash bonuses for opening up accounts. Banks run promotions like this all the time, so grab some real cash quickly if you're in need. It won't break the bank (no pun intended) but it will give you a quick $50 or $100 -- maybe even more -- when you really need it. You might need to deposit a minimum amount of cash (usually in the thousands) in order to qualify for these types of accounts (but not always).
Double check yourself, before you double wreck yourself. Make sure everything you send to a company, whether a résumé, an email or a portfolio, is good to go. Double check your grammar and wording, and for God’s sake use spell check! This is especially important when it comes to the company’s name. Don’t spell their name wrong and be sure to type it how they type it (e.g. Problogger, not Pro Blogger).
Regardless if you need to earn some fast cash or we're just talking about making money in the grand scheme of things, there's an important psychology that needs to be mentioned before getting into the strategies. If you study Freud's model of the mind, you'll discover the Psychic Apparatus. It's the three-part construct in your mind that controls all of your behavior.