I first read the following text from a blog years ago (for the writer of that blog, I am sorry I cant recall your name), and since then I always placed it where I work:
Be humble. Always first presume that you're wrong. While developers do make mistakes, and as a new hire you should certainly assist others in catching and correcting mistakes, you should try to ensure that you're certain of your observation before proudly declaring your find. It is enormously damaging to your credibility when you cry wolf.
Be discreet with constructive criticism. A developer is much more likely to be accept casual suggestions and quiet leading questions than they are if the same is emailed to the entire group. Widening the audience is more likely to yield defensiveness and retribution. The team is always considering what your motives are, and you will be called on it and exiled if you degrade the work of others for self-promotion.
The best way to earn credibility and respect is through hard work and real results. Cheap, superficial substitutes - like best practice emails sent to all, or passing comments about how great it would be to implement some silver bullet - won't yield the same effect, and are more easily neutralized.
Actions speak louder than words. Simply talking about implementing a team blog, or a wiki, or a new source control mechanism, or a new technology, is cheap. Everyone knows that you're just trying to claim ownership of the idea when someone eventually actually does the hard work of doing it, and they'll detest you for it. If you want to propose something, put some elbow grease behind it. For instance, demonstrate the foundations of a team blog, including preliminary usage guidelines, and a demonstration of all of the supporting technologies. This doesn't guarantee that the initiative will fly, and the effort might for the naught, but the team will identify that it's actual motivation and effort behind it, rather than an attempt at some easy points.
There is no one-size-fits-all advice. Not every application is a high-volume e-commerce site. Just because that's the most common best-practices subject doesn't mean that it's even remotely the best design philosophies for the group you're joining.