Just like you might think in order to make money online fast the one ingredient that is the same as offline is the fact that you will require something to sell. There are of course other ways that don't require something to sell directly but for most people this doesn't enter the picture. For instance if you collected money monthly as membership sites do, you would have still needed the service to sell in the beginning.
So if the idea is to be quick about it then you will also require just where online you will be selling this product or service. For instance you could build a mailing list but this would not qualify as fast as far as making money fast goes so you will need to look at things with instant connections with people or prospects like eBay or the social media networks.
One interesting and effective method that many people are overlooking is email marketing. Not the traditional kind of mailing to lists of hundreds or thousands but direct email. With direct email you research prospects online, going to their websites, finding good prospects that could use your services and then contacting them one by one making your proposition or offer. By mentioning their website you can avoid your message looking like spam or bulk email because it's not.
Another very popular way to contact prospects in realtime is to use social media sites like Facebook and Twitter. These networks allow fast growing of contacts or "friends" as they are commonly referred to.
As you see even though we touched on finding something to sell in order to make money online fast there is more involved. You will need to decide where and how you will sell your product or service as well. Chances are that this is something though easy to implement once instructed, you will likely need a competent guide to aid in insuring success.