The term startup is synonymous with crisis. If you are in a startup and are not in a crisis at least once a year (more like every six months), then I'd submit that something isn't right. If your organization is taking the risks - on the product, go-to-market or investment side or you're being too aggressive in certain areas... you're going to hit a crisis. Either way, hitting a crisis is a sign you are doing something right.

Success depends on the team's ability to successfully navigate the crisis and put it to bed, completely so that it doesn't loom bigger 12 months later only now its bigger, badder and indeed, life threatening to the company.

The team, CEO, leadership,employees and investors all have a part in managing crisis. As a startup you actually have an advantage over larger organizations. Your organization 's ability to change is much more facile than a larger enterprise. Large companies don't do change well. Hell, many of them don't do change at all... (see where they end up!). Effective crisis management relies on the following:

1. Assessment: assess the situation quickly and effectively by applying the most effective resource to analyze the problem... Don't rush but don't take too long! And most importantly, apply the right resource. Don't be shy about going outside the four walls of your company to find an expert resource in the affected area. If this is a customer issue - engage with the customer immediately. Even if you have nothing of substance to say to them... engage! Let them know that you are working on the issue and make sure that there is a regular cadence of communication. The last thing you want to do is to let a crisis impact a positive customer experience.
2. Advice: even if you leverage an outside source to analyze the situation, leverage your and your investor's networks to find additional expert opinions. Another Point of View will take you far in terms of understanding the issue and generating possible solutions. Also, seek opinions from outside your vertical/space. You will be amazed at how the different perspectives from folks in different industries will drive you toward effective solutions.
3. Action: execute on the plan you have laid out and assess its effectiveness frequently and with regularity. As part of this step make sure you lay out clear KPIs (Key Performance Indicators) for you, the affected portion of the organization and the third party if its a customer or partner. KPIs for customers and partners should take the form of; "Customer/Partner agrees that this issue is resolved if X,Y and or Z are addressed." It doesn't have to be in writing but you want your customers and partners to agree to the remediation you will be taking in order to resolve the issue.

Startups fail when they can't easily adapt to changes in the marketplace or the realization that the facts have changed or they keep heading down the wrong road. Therefore, there's a step 4: Repeat as necessary.