Be nice to strangers. Be nice even when it doesn't matter.

People always make the mistake of calling an idea small or stupid because they don't understand how it's going to evolve.

Sometimes people think Y Combinator has big ideas about themes. But really, we just fund the best startups.

If you go to a paintball subreddit, paintball companies can advertise to you.

What is OK is to spend money for productivity. What is not OK is just to light money on fire.

Maybe I am a bit unusual here, but I am less stressed if I have my phone with me. Because I can spend like an hour in the morning taking care of everything instead of I sit there and wonder what I missed or wonder what's happening. So it's way less stressful for me to just answer my phone.

If a company is profitable, the founder is in control. If it's not, investors are in control.

Ideas are cheap and easy, and there are a lot of them.

I think that inexpensive sources of planet-friendly energy are one of the most important things for us to pursue.

Startups on the inside are always badly broken.

I suppose if I didn't have Loopt, I'd have to, I don't know, pick up the phone and just start calling people, a lot more texting and certainly more Googling.

Set a clear, easy-to-understand vision for your company, and make it be a mission people believe in.

If you compromise and hire someone mediocre, you will always regret it.

Many founders hire just because it seems like a cool thing to do, and people always ask how many employees you have.

AI will probably most likely lead to the end of the world, but in the meantime, there'll be great companies.

I have plenty of investments that I wish I'd never made. But the model is to lose money on a lot of investments and then make 1,000X or 10,000X on an investment.

Companies generally work better when they are smaller. It's always worth spending time to think about the least amount of projects/work you can feasibly do, and then having as small a team as possible to do it.

Check-ins are cool, but kind of a pain.

That culture of frugality and discipline is really important for the Y Combinator mindset.

The hard part of running a business is that there are a hundred things that you could be doing, and only five of those actually matter, and only one of them matters more than all of the rest of them combined. So figuring out there is a critical path thing to focus on and ignoring everything else is really important.

If you have the opportunity to go be an early employee at a company that's just going crazy, and you believe it's the next Facebook or Google, you should go join that company.

Everyone is looking for the hack, the secret to success without hard work.

I love working with really early stage startups where the outcome is still in doubt. Maybe they'll go on to greatness, or maybe they'll never get off the runway at all.

The market for local advertising is in the billions.

I don't invest in companies where my mental model is that they need to get themselves acquired in the next few years - or ever.

The biggest part of Loopt is about discovering the world around you, never replacing a social experience - only adding to it.

Don't let yourself make excuses for not doing the things you want to do.

Whoever Boost works with, Sprint will work with. And whoever Sprint works with, Verizon and AT&T will as well.

Communication services need interoperability to succeed - and Loopt is the first such service since SMS that is available across all major U.S. wireless carriers.

All throughout my life I have been deeply immersed in startups, either because I was running one or investing in them or helping them.

I don't think people spend nearly enough time thinking about what they like and what they're good at.

Asking what I'd do without Loopt is almost like asking what I would do if I didn't have a smartphone because the feature set has become the norm for me.

There's this famous observation that I totally believe: Great startup ideas are the ones that lie in the intersection of the Venn diagram of 'is a good idea' and 'looks like a bad idea.' So you want most people to think it's a bad idea and thus not compete with you until you get giant. But for it to secretly be good.

Loopt wouldn't have happened without Y Combinator.

Traditional local advertising is not what retailers want. They want not just for you to see an ad - they want you to come into the store, to be a repeat customer and to spread the word.

Making money is often more fun than spending it, though I personally have never regretted money I've spent on friends, new experiences, saving time, travel, and causes I believe in.

If you wanted to build an Internet startup in 2005, you had to buy your own servers and hire someone to manage it. Now, that's unheard of.

The start-ups that do well are the ones that are working all the time.

Whether or not money can buy happiness, it can buy freedom, and that's a big deal. Also, lack of money is very stressful.

Many of the companies in the mobile location space are trying to figure out different ways to tie what they're doing to commerce.

Tech companies tend to do tech best.

The way to really scale a venture firm is with software.

Technology magnifies differences, and it's been replacing or obviating jobs for a long time. But what happens as that case accelerates? I'm not one of these doomsayers who says, 'There will be no jobs.'

It's easy to say, 'I'm going to build something that already exists,' but it's difficult to clearly and succinctly describe something new.

All the reasons that have made software so successful are beginning to happen with hardware. So much can be done so quickly, prototyped so rapidly, and the costs are so low.

If you ask a founder how their company is doing, they always say, 'Oh it's great. We're totally crushing it,' and that's almost never true.

The Loopt mobile app is all about giving you the latest local deals and insider tips.

One of the things we urge Y-Combinator companies to do is to have profitability in grasp. If you need to get profitable before your A round of money, you ought to be able to do that.

The crowd's a really powerful force on the Internet, and people finally understand how to harness that.