No one ever said starting a business is easy. Even with today's breakthrough technologies, getting up and running--much less scaling and growing--is still infinitely difficult. So why not take some advice from those who've been there, done that, and found success?

We've pulled together some of the best advice from this year's 30 Under 30 Rising Star judges, who include: Phil Libin, a senior adviser at General Catalyst and co-founder of Evernote and All Turtles; Sarah Kauss, CEO and founder of designer-water-bottle company S'well; Spectacular Blue Smith, the social-media guru behind the Adwizar agency; and Jen Rubio, a 30 Under 30 alum and co-founder of luggage brand Away.

What is your best advice for young entrepreneurs today?

Sarah Kauss: Think big and be bold. So many entrepreneurs have a big idea that seems crazy. But that's how it starts. It is not going to come to life unless you are willing to take a risk, be bold, and put it out into the universe.

What advice do you wish someone had given you when you were just starting out?

Phil Libin: Everything is equally hard. Building a great company is just as hard as building a sh--ty company, which is just as hard as sitting on your couch all day--in the sense that it all costs roughly the same number of hours of consciousness, the same number of heartbeats, the same number of synapses firing. Everything is equally hard, but not everything is equally meaningful. Spend the effort on meaningful things.

What is the biggest missed opportunity you're seeing today that would-be entrepreneurs should jump on?

Jen Rubio: One of the biggest missed opportunities is just time. Start now. That idea you've had in the back of your head for the past several months (maybe years)? Just do it. There's no playbook. You won't have all of the answers. And you're going to make some mistakes along the way. The longer you wait, the further you'll have to fall if you fail, and if you're going to succeed, you'll need to be comfortable with a bit of risk anyway.

What is the most common mistake you see young people make and how can they avoid it?

Libin: They accept conventional wisdom and get victimized as a result. Every time someone says, "That's standard," or, "Those are market terms," or, "It's always been like this," call bulls--t. Conventional wisdom didn't get to be conventional because it's true. It did so because it's easy to repeat.

Where are you or what are you doing when you get your best ideas?

Spectacular Blue Smith: I get most of my best ideas as I'm meditating. My morning ritual is to meditate as soon as I wake up. This is before looking at my phone, checking emails, brushing my teeth, etc. Once I'm done meditating, I have a plethora of amazing ideas that I write down on my to-do list to complete within the next few days. I got my idea to launch Adwizar's GrowthX--a viral program to help aspiring talent and personality brands become famous on social media--after meditating. Feels like a superpower.

What's the one job interview question you always ask?

Rubio: "When was the last time you failed?" The answer will show me two things: one, how you feel about failure, and two, how you deal with it. We use it as an opportunity to iterate and grow.

What book should be on every big-thinking entrepreneur's nightstand? Why?

Kauss: I recommend Patty McCord's latest book, Powerful: Building a Culture of Freedom and Responsibility. Her point of view helps you rethink some of your current practices, encourages more strategic thinking, and empowers action-driven teams through policies.

Smith: Every entrepreneur should have a book named Disrupt You! by Jay Samit. This book really changed the way I think in business. It's one of my top three entrepreneur books of all time and my first recommendation to read for all of my mentees.

Rubio: Mindset: The New Psychology of Success by Carol Dweck, which shows how our thoughts have the ability to determine how we deal with obstacles entrepreneurs can face.

Libin: If it's a small nightstand, The Clock of the Long Now by Stewart Brand. Chapter 7 explains pretty much everything you need to know about the world.

If it's a large nightstand, The Three-Body Problem trilogy by Cixin Liu. When the next generation of Chinese entrepreneurs rewrite the world over the next couple of decades, these are the books they'll be quoting from. They'll be what Star Trek, I, Robot, and Lord of the Rings were for English-speaking nerds.

Also, stop keeping books on your nightstand. Read when you're wide awake, not as a way to fall asleep.