Each Monday, we're putting together the top five lessons from the previous week's Y Combinator How to Start a Startup cla** lectures. Click on the highlighted text for additional commentary and insights. 1. To Excel at a Startup... You need a great idea, a great product, a great team, and great execution. These overlap somewhat, but I'm going to have to talk about them somewhat individually to make it make sense. You may still fail. The outcome is something like idea x product x execution x team x luck, where luck is a random number between zero and ten thousand. Literally that much. But if you do really well in the four areas you can control, you have a good chance at at least some amount of success. 2. Great Ideas Often Look Bad at the Beginning The hardest part about coming up with great ideas, is that the best ideas often look terrible at the beginning. The thirteenth search engine, and without all the features of a web portal? Most people thought that was pointless. Search was done, and anyways, it didn't matter that much. Portals were where the value was at. The tenth social network, and limited only to college students with no money? Also terrible. MySpace has won and who wants college students as customers? Or a way to stay on strangers' couches. That just sounds terrible all around. These all sounded really bad but they turned out to be good. If they sounded really good, there would be too many people working on them. 3. Build What Your Customers Love Your job is to build something that users love. Very few companies that go on to be super successful get there without first doing this. A lot of good-on-paper startups fail because they merely make something that people like. Making something that people want, but only a medium amount, is a great way to fail, and not understand why you're failing. 4. CoFounders Count... A Lot Cofounder relationships are among the most important in the entire company. Everyone says you have to watch out for tension brewing among cofounders and you have to address is immediately. That's all true and certainly in YC's case, the number one cause of early d**h for startups is cofounder blowups. But for some reason, a lot of people treat choosing their cofounder with even less importance than hiring. Don't do this! This is one of the most important decisions you make in the life of your startup and you need to treat it as such. 5. It's All About Execution The CEO, people ask me all the time about the jobs of the CEO. There are probably more than five, here are five that come up a lot in the early days. The first four everyone thinks of as CEO jobs: set the vision, raise money, evangelize the mission to people you're trying to recruit, executives, partners, press, everybody, hire and manage the team. But the fifth one is setting the execution bar and this is not the one that most founders get excited about or envision themselves doing but I think it is actually one of the critical CEO roles and no one but the CEO can do this.