Believe it or not, all kindergarteners do not enter your doors equal in shape, size or readiness.
The first couple of weeks of school is the perfect time for pre-assessing for readiness and understanding. Allow for exploration of centers, materials and manipulatives and you can't imagine what you find out. Instead of spending two weeks teaching shapes, in those first few days of school, you might discover that most of your class already has already mastered that topic. Those that have mastered them can move on and expand their understanding.
I use all of these and more (observations, role play, conversation, etc.) but a check lists is most definitely my tool of choice. I have check lists for letter recognition, counting, sight words . . . but the ones I use the most are my common core checklists. I keep them separated by ELA on one clipboard and Math on another. It is easy for me to observe a child making a rectangle from two triangles and quickly mark it off on my checklist or add the date of observation.
These are what my poor checklists looked like at the end of the year, but you can see they were lovingly used. I paced them out by quarter so that I could quickly see how to tier for a specific skill and how the class was pacing for the year to meet all standards. This system might not work for everyone, but it was perfect for me. It kept me on track and it was a quick visual of where all my students were at any given time. I have since revamped my checklists, added the common core coding that I had had written in by hand previously, and worked out the pacing so it flowed better from my experience. This is what I have to work with this year:
If you'd like to find out more about these EDITABLE checklists, you can click on the picture above or find the math version HERE and the ELA version HERE. I have them paced out for each quarter of the year or separated by standard in both color and black and white.
I hope you're able to take the time during these first weeks of the school year to really get to know your students and start mapping an initial plan for their instruction. The one thing you can say about differentiated instruction, it's never boring. We are always assessing, adjusting and instructing . . .but the time and effort is well worth it when you have the payoff of successfully engaged students, neither bored because instruction is too easy nor frustrated because it is too difficult.
Good luck and let me know how it goes for you.