In this study, I documented, analyzed, and compared the thought processes of six high school science teachers during twenty minutes of planning for NGSS-aligned instruction. Teachers' thoughts were captured using a virtual revisit think-aloud protocol and their thoughts were analyzed and compared using a novel tool called a thinking web. A narrative of each teacher's planning process is provided in this paper along with each teacher's thinking web. My analysis produced a list of thirty-five different thought types within the three categories of antecedent planning conditions conceptualized by Shavelson and Stern (1981): nature of instructional task, information about students, and context of instruction. This paper offers this taxonomy of thought types with definitions and examples as well as a replicable procedure for documenting and analyzing teacher thought processes during planning for NGSS-aligned instruction. This procedure can be used for professional development by pre-service and in-service teachers, instructional coaches and coordinators, administrators, education faculty, and educational researchers. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]