- is the scope well defined?

- do I understand the value add and agree with it?

- do I feel as if all stakeholders are aligned and adequately involved?

- do I think the team can pull it off ?

- do I think the mood and style fits myself?

- do I think the timelines and budgets are realisitc?

- do I agree with the level of transparency from management?

Etc etc

Ask yourself these questions - and more - and you will discover the answer for yourself.

In the end listen to your guts.

One important nuance: A project can be a major fail overal but a big success for you. Big check, new knowledge, rich connections...

- Does the customer have an IT org capable of fulfilling basic tasks you won't be authorized to do (app / db access, AD / rights modification, firewall adjustment, AV adjustment) in a timely manner?

- Can the customer provision necessary machines in a timely manner? If using VMs, is the virtualization team competent with their chosen platform?

- Does this project directly threaten the job of anyone whose blessing / help is required to successfully deliver the project?

- Is your leadership / your customer champion intelligent and willing enough to say "No" to scope creep when the customer gets excited?

- Do the PMs attached to the project have a basic understanding of how software is built and the systems involved?

- Does their management understand the actual processes being interacted with? (Major red flag! If their management / leaders say things in meetings that demonstrate a basic lack of understanding in what their own people do, run)