You first have to decide what kind of startup you're looking for. Do you want to be hire 1-10, 10-50,50-100, or 100+? Each of those company sizes is a substantially different beast and depending on which one is more suitable to you the other questions change dramatically.
If you're looking at the 50-100 range then the startup is obviously more mature and the nature of the company isn't as important so much as the work you'll be doing. If you're looking to be hire 1-10 then the company itself is a lot more important, especially the founders.
Let's assume you're looking to join a smaller team. If that's the case then I'd concentrate almost everything on the founders. Ultimately it comes down to trust. Do you trust these people to focus on important matters? Do you trust them to be fair and mature about tough decisions? Do you trust them to treat you and your coworkers right?
For many people this can be a difficult thing to gauge and it's made especially more difficult since the founders will be actively trying to sell you and therefore make themselves look better.
Ultimately there are some high level filters that can help carve out a lot of options and save you a lot of time. And these are actually the same kind of filters that investors apply:
Are they a YC company?
What is the experience of the founders? Have they done a startup before? Do they have an "in" for the space?
Does the company have traction?
The reason why I put YC company first is that pg and co are going to be better than most people at picking winners. So if you limit your choice to YC companies then you're going to have a much lower chance of joining the wrong company. I say that from some bias as being a founder of a YC company, but also because I've met many of the founders of other YC companies, and it's just crazy how many of them are awesome and trustworthy.
If you're looking at the 50-100 range then the startup is obviously more mature and the nature of the company isn't as important so much as the work you'll be doing. If you're looking to be hire 1-10 then the company itself is a lot more important, especially the founders.
Let's assume you're looking to join a smaller team. If that's the case then I'd concentrate almost everything on the founders. Ultimately it comes down to trust. Do you trust these people to focus on important matters? Do you trust them to be fair and mature about tough decisions? Do you trust them to treat you and your coworkers right?
For many people this can be a difficult thing to gauge and it's made especially more difficult since the founders will be actively trying to sell you and therefore make themselves look better.
Ultimately there are some high level filters that can help carve out a lot of options and save you a lot of time. And these are actually the same kind of filters that investors apply:
Are they a YC company?
What is the experience of the founders? Have they done a startup before? Do they have an "in" for the space?
Does the company have traction?
The reason why I put YC company first is that pg and co are going to be better than most people at picking winners. So if you limit your choice to YC companies then you're going to have a much lower chance of joining the wrong company. I say that from some bias as being a founder of a YC company, but also because I've met many of the founders of other YC companies, and it's just crazy how many of them are awesome and trustworthy.