I suspect that you already know much or all of this, but there are some things that cry out to be said.
- Cherish your design process. You're going to make mistakes. You're going to have to fix them - and for each of those mistakes, the earlier in the process you can catch them, the faster and easier they are to fix.
- Alongside that, write code to make it easy to fix things. Write code to make it easy to change your mind. Copy/paste feels easy at first, but if you have the same piece of code in four different places, and then figure out that you did it wrong, you have four places to change the bloody thing (and four places to mess it up as you change it). Try not to have the same piece of code in more than one place at a time, and if you think there's any chance that you might want to change something later, keep that in mind as you're designing it. Don't hard code anything you can easily put in a properties file, etc, etc, etc.
- If you've never made a game before, or never made a game of this type before, or whatever, build an extremely stripped-down version first. Don't expect to reuse any of the code (if any of it is salvageable, that's great, but it's not the point). Making the really stripped down version will teach you a fair bit about what goes into make the real thing, and you can take that back to the design process - and if you find that the code you make *isn't* reusable, it's one of the more efficient ways to figure out that sort of mistake before it's deep in the code you're actually using. Also, if it's even remotely playable, you can stick it out there for people to play. That's always nice.
- Cherish your design process. You're going to make mistakes. You're going to have to fix them - and for each of those mistakes, the earlier in the process you can catch them, the faster and easier they are to fix.
- Alongside that, write code to make it easy to fix things. Write code to make it easy to change your mind. Copy/paste feels easy at first, but if you have the same piece of code in four different places, and then figure out that you did it wrong, you have four places to change the bloody thing (and four places to mess it up as you change it). Try not to have the same piece of code in more than one place at a time, and if you think there's any chance that you might want to change something later, keep that in mind as you're designing it. Don't hard code anything you can easily put in a properties file, etc, etc, etc.
- If you've never made a game before, or never made a game of this type before, or whatever, build an extremely stripped-down version first. Don't expect to reuse any of the code (if any of it is salvageable, that's great, but it's not the point). Making the really stripped down version will teach you a fair bit about what goes into make the real thing, and you can take that back to the design process - and if you find that the code you make *isn't* reusable, it's one of the more efficient ways to figure out that sort of mistake before it's deep in the code you're actually using. Also, if it's even remotely playable, you can stick it out there for people to play. That's always nice.