Ask HN: As a potential contractor, should I sign an NDA?

I guess the more appropriate question is, what are the 'dos and donts' of NDAs that I should look out for? I just got one that has a 3-year non-compete/non-disclose term. That seems a bit excessive, given that I don't know what the idea is and I do consulting for other people. I am concerned that something like that will prevent me from working on other contracts or engaging clients with similar projects in the near future. I have no intention of stealing any trade secrets of IP, but what is a realistic solution so both sides can feel protected - especially given that I know that we, in the software dev world, don't like NDAs/patents/etc.?