While I normally don’t like to play on words, or play on semantics this is one time it is essential. First we have to define the word best. Merriam-Webster Dictionary Online defines the word best as: "excelling all others." So we can say that a best practice is one that excels all other practices. It’s not just a good practice, or a great practice, or a better practice, it achieves the status of being the practice that is above all other practices.
I have often heard it said that “the pill that cures one person can kill another person.” This is especially true when it comes to best practices. What works for you, your team, division, corporation, etc., can bring another person or team to a screeching halt. So, first, when we say “best practice,” we need to look at the context in which it is being used. For example, the best practice you use for putting code into a repository is to check the code in at the end of the day, that way, no more than one day's work would be lost. That works great for a team of developers working on text-based code. Where as, if you were working with CAD, it may not be feasible as the file sizes would grow exponentially.
The next thing to consider for best practices is the content of the practice. If it is truly a best practice, anyone at your organization could use it the same way that you’re using it. If it is tweaked in any way, it loses its moniker of “best practice” and simply becomes a practice, maybe a good or better practice, but not to the level of best practice. The content of the best practice should also stand the test of time and not be specific to a particular technology or methodology. If it is, then feasibly within a year it could lose its best practice designation and even fall below the realm of good or recommended practice.
This brings up a point about best practices that needs to be addressed. Who determines if something is a best practice? If left to individuals or teams, you run the risk of everything being a best practice that comes from that person or team. We must look at the motive behind something being deemed a best practice. This is not to say that everyone who deems their idea a best practice has ulterior motives; however, it does occur and for a variety of reasons. Rather than go into the laundry list of reasons, let's suffice it to say that the biggest reason this can occur is office politics. Getting the right group assembled that can determine what reaches the standards of being a best practice can be difficult, but not impossible. It requires people with a broad knowledge of the organization who see the big picture and whether or not the best practice could be implemented throughout the organization. This group will, unfortunately, have to inform people that their best practice is simply a good or better practice, but not to the level of a best practice. This can result in hurt feelings or anger. The other danger is that the group determines everything a best practice, thus causing issues as the practices deemed best begin to inflict irreparable damage to groups who try to implement them.
In conclusion, I am not advocating that there are no best practices. I am advocating that very few practices rise to that level and that most practices be labled good, great, or better. Your team, group, division, or industry will have to determine for yourselves what is a best practice, just be aware of the pitfalls in declaring something “best.”