Great question, John... it's hard to know where to start, right?
The first thing to do is to establish what your budget will be for improvements, as that will be the primary constraint on what improvements you would want to implement.
Complementing that effort, you should ask your municipality in Tempe what monetary incentives are available to you there.
- More than likely the incentives will be available primarily for energy upgrades.
- Incentives and rebate programs enable you to either reduce the expenditures you make for improvements or increase your budget in order to add additional improvements.
Start with an energy audit
My own recommendation is that you have an Energy Audit done on your home as well. Often the incentive programs will require that an audit be done on your home.
- Google "HERS Raters" in your area and you should be able to find people who can help you.
- In addition, if there is an energy upgrade incentive program available to you, the folks who administer the program will be able to help you work on getting an energy audit performed.
Finally, my last "first thing" to do would be to go to the USGBC's best resource for greening existing homes, the REGREEN program.
The REGREEN website has incredible tools for assisting you in learning what improvements you can make to green your home.
Best of luck, and enjoy the adventure!