It's all about finding and riding a wave to the end. Rinse. Repeat. You've got to be aware of all your surroundings. How's the tide? The weather forecast? The temperature both in and out of the water? Is the area crowded or do you have room to maneuver?
When you start working with platforms like Google Adwords, Facebook Ads, Twitter Ads and more you need to be acutely aware of the your surroundings. Which platforms have accessibility to the most people? Which platforms are your target demographics using the most? What are the targeting capabilities of the platform? What keywords can you afford to bid up? Which platforms are oversaturated? Which ones are underpriced?
You also need to make sure your ads don't suck. If you have weak copy, visuals, links, or calls to action you're going to face plant. Hard.
Be ready to eat sand for a while. Like anything, there is a learning curve with digital advertising. It may seem easy from the outside, but you can't just come up with what you think is a killer advertisement, slap it on the internet, and expect money to fall from the heavens.
Ask for feedback. Get in the shoes of your customers and discern if what you're throwing out there would ever convince them to click or dive deeper with you. Don't be afraid to ask for help. There are others out there who have more experience and knowledge that they want to share with others. All you have to do is ask.
Also be aware that the advertising complex as a whole is broken. We're forcing ads on people who don't want what we have. It's an uphill battle and the landscape is constantly changing. Be on the leading edge and you might have a chance.