If you ask me, I'll tell you a great developer
Plans before coding
A great developer takes the time to plan an approach before designing or coding. A great developer knows that the time required to do so will be more than paid back by the time saved by getting it more right the first time. A great developer plans all scales of work, from envisioning multiple versions of a product to writing or modifying a small method.
Always knows why
A great developer always knows exactly why they wrote a particular line of code, and why they wrote it the way they did. A great developer writes code because that code is the best choice for a particular situation, not just because it is the canonical implementation. A great developer codes consciously.
Writes situation-appropriate code
Any developer can write code. A good developer writes solid code. A very good developer writes elegant code. A great developer writes code that is both solid (compact, well constructed) and elegant (precise, simple, graceful, polished). More importantly, a great developer can tell when elegance is not worth the effort.
Deviates where and when necessary
A great developer not only knows the canonical implementation but understands it is the canonical implementation. A great developer can tell when the canonical implementation is not the best answer for a particular problem.
Knows when not to change code
A great developer knows that changing code is sometimes worse than fixing it. Fixing a bug may cause too much instability elsewhere in the product, for example. Messy code whose function is not well understood shouldn't be rewritten until there is sufficient time to ensure its function is well understood. A great developer understands the tradeoffs involved between changing code versus leaving it as is.
Approaches debugging scientifically
A great developer knows that debugging is a science not an art and approaches it as such. A great developer formulates a theory as to the cause of the problem, determines a method for proving the theory wrong, performs the experiment, and observes the result. A great developer records this information and uses this data to guide further work.
Walks through their code
A great developer knows that they don't really know their code until they've stepped through it. A great developer sets breakpoints on every line of code as it's written so they know which lines haven't been hit.
Knows the language and platform intimately
A great developer knows the programming language (and platform) in use inside and out. A great developer knows why each construct (API) was included in the language (platform) and why other constructs (APIs) were left out. A great developer disagrees with certain aspects of the language (platform) but understands why those aspects work the way they do. A great developer knows what the language (platform) can do, what it can't, and how to achieve the same effect through other means.
Groks the tools
A great developer knows what the available tools are and how to use each of them. A great developer knows that not every tool is appropriate for any particular task. A great developer knows how to abuse the tools to produce results hard or impossible to accomplish via "approved" uses.
Improves the tools
A great developer knows that their tools can always be improved. A great developer prefers to get these improvements from elsewhere so they can concentrate on solving the customer's problem. A great developer recognizes when it is simply faster or more efficient to write a tool themselves. A great developer constantly looks for opportunities for increasing their productivity.
Knows when to ask for help
A great developer takes pleasure in a challenge. A great developer, then, enjoys banging up against a brick wall and slowly breaking through it. Some walls are thicker than others, however, and sometimes the wall has a developer-size hole that the developer continually manages to miss. A great developer realizes when it's time to ask for help and does so. A great developer knows who to ask for help. A great developer knows there isn't any shame in asking for help.
Always has a side project going
A great developer is never completely satisfied by the current project. A great developer is always also working on a (probably many) side project meant to investigate an idea, understand a language or library feature, automate a process, or otherwise itch a scratch the primary project isn't satisfying.
Doesn't make assumptions
A great developer actually does make assumptions, but a great developer doesn't stop there. A great developer inspects the assumption, then researches that assumption into knowledge. A great developer does this not just for their own assumptions but for assumptions other people make as well.
A great developer documents everything. A great developer strives for self-documenting code but knows that some amount of documentation is always required. A great developer knows that documentation need satisfy only two goals: educate the current audience, and preserve enough knowledge about the topic that the current audience can expand the documentation as necessary for any future audience.
Follows coding standards
A great developer has internalized and continuously uses a set of coding standards. A great developer may not be able to recite the standards word for word, but when asked about any particular point the correct answer is immediately forthcoming. A great developer writes conformant code without the aid of verification tools, but always runs those tools as a backstop.
Uses version control
A great developer knows that version control is as important for personal projects as for enterprise projects. A great developer version controls everything.
Makes lots of small checkins
A great developer knows that version control is most useful when code is modified via small checkins that each contain a single logical change. A great developer strives to check each change in independently from each other change.
Tests their own code
A great developer is embarrassed when someone else finds a bug in their code. A great developer thoroughly tests their code before checking it in. A great developer doesn't pretend to be a great tester but does strive to be considered a good tester.
Has passion for their customer
A great developer understands what the customer needs to do and how the customer wants to use the product. A great developer looks beyond the customer's needs to see how the product can revolutionize the customer's tasks. A great developer promotes the customer's point of view throughout the product cycle, from the first nascent product vision through specifying and implementing features to cutting features and triaging bugs to product release and ongoing maintenance. A great developer helps the rest of the product team understand the customer as well as they do.
Has great judgement
A great developer understands the business case for the code he is writing. A great developer uses this as a basis for judging what code to write and what code should not be written. A great developer uses this as a basis for deciding when to write code and when writing code is not the right thing to do. A great developer uses this to balance designing for the future against the need to get something done in a timely manner.
Has no ego
A great developer values the praise of their customer over the praise of their peers. A great developer wants to do the right thing but doesn't much care about being right. A great developer brings their reasoned opinion to design and coding discussions but listens carefully when alternatives are offered, searching out and examining the details of these other options. A great developer appreciates suggestions for improving their code or design. A great developer knows they will write bugs and appreciates it when bugs are brought to their attention. A great developer follows a process because the process protects them from themselves.
Makes time for training
A great developer knows that the only way to continue to be a great developer is to never stop learning. A great developer doesn't limit this education to programming-related topics, either, but also researches testing, program management, marketing, and anything else that is remotely related to the process of creating software.
*** Comments, questions, feedback? Want a fun job on a great team? Send two coding samples and an explanation of why you chose them, and of course your resume, to me at michhu at microsoft dot com. I need testers, and my team needs a data binding developer, program managers, and a product manager. Great coding skills required for all positions.