Here is the last entry on being a GIS Developer. See Part 1 and Part 2.
36. You should realize that you can't do everything. Ask for help.
37. Learn other tools that can help you do your work. Learn tools that help you code, design, debug, communicate (i.e. MS Office), and manage (i.e. MS Project), etc.
38. Always be cognizant of the cost of things. It may sometimes be cheaper to buy what you need as opposed to developing it.
39. Understand licensing issues. Sometimes a solution to a problem may not be feasible just because the way a company has structured their licensing.
40. Learn to evaluate alternatives. A little thinking ahead can save a lot of time. This not only applies to architecting a new GIS, but also in spatial analysis.
41. Always be weary of hype especially from vendors and even from yourself.
42. Remember, under sell and over deliver. Set expectations.
43. Sometimes the performance of your app will be less than desirable but realize that it may be the data or the network, not your code. Or it may be your code and don't be shocked if you have to re-write something.
44. Just because ESRI (or any other vendor) does it this way doesn't mean it's the best way in general or the best way for your organization or for your app, or for you.
45. Always do the best you can with what you have. You may not have the latest version of ArcGIS and have to make due and develop a custom tool that no one else will ever use.
46. Try to be cognizant of how much work you will create for others. Always try to make it easier.
47. Commit yourself to helping the GIS community as a whole. Be a part of GIS day, help other users via online forums, etc.
48. Keep notes of what you've learned and what you must do and share it.
49. Avoid bad mouthing a predecessor. You don’t need to validate yourself by tearing down those that came before you.
50. Sometimes you will be the GIS superstar because everything came together with the right app and right people and at other times you won’t be. Sometime things just won’t work out and there’s not much you can do about it. Sometimes fortune plays a huge role in your success and at other times misfortune is your worst enemy. Hopefully, however, your successes will be more than the failures.
51. Don’t milk a project. You should always get the project done as quickly and efficiently as possible.
52. Realize that the technologies you know now will be replaced in a few years. This not only includes the technology, but also the way in which you implement and develop software.