To show students where to sit each week, I use name cards. Each name card is a full sheet of paper folded in half so it can rest on top of the stand and can be viewed from both in front and behind. These are color-coded by instrument.
At the beginning of the year with first-year students, I use these during small groups, both so students know where to sit and because I am still learning names. At the beginning of the day, I have the cards stacked in the order I'll be seeing kids during the day and within easy reach (on the piano bench) so that I can quickly switch name cards at the transition time. That is an incentive for me to learn names sooner rather than later, as it takes a few moments to get those organized at the beginning of the day (or end of the day the previous week if I'm on top of things). I do make an effort to switch up seating each week, just for variety's sake.
I also use these every week for full orchestra. The color-coding helps kids quickly locate their instrument's section and then their own name. Again, I do make an effort to switch up the seating each week. I want students to experience playing in the front, middle, and back of the section and with different stand partners too.
Except for a concert seating chart (which goes into effect about three full orchestras before the concert) where the students do stay in the same spot from one week to the next, I do not write out the seating chart each week. I just do my best to keep scrambling up stand partners and who's sitting where. When I'm really organized, in the folder where I store the name cards, I will jot down anyone without a stand partner due to having an odd number of students so that I can make sure someone else will be the singleton next week.
Students who have forgotten their instrument and need to borrow a spare will be seated together so they can share the spare without disrupting the students around them. If students do have to share an instrument because I can see their spot on the instrument rack is empty, I write the two (or three...hopefully not more) names on a piece of scrap paper and tape it to the case of the spare so both students know who they'll be sharing with and it doesn't take any class time for me to explain. I also pull out the names of students who are absent that day from the stack and set up accordingly so there aren't any empty chairs in full orchestra.
Every once in a while students will walk into the room for full orchestra with no name cards out and a "Seating is free choice today :)" note on the board. That generally happens the week after a concert.
The front side (that I see) includes more information such as the student's full name and teacher's name in smaller font at the bottom. If students try to switch name cards without me noticing, a hint is that they put the card on the wrong way and I see the side with just the first name :)
To actually create the name cards without having to type up everyone's name one by one, I use the "Step-by-Step Mail Merge Wizard" feature in Microsoft Word and pull the information directly from my roster, which is saved as an Excel sheet. I double check the document before printing and add last initials for those students who have someone else with the same first name in the same orchestra. The document is already organized by instrument (since that's how my roster is set up), which makes color-coding printing simple.
Name card template (Word document)
Enjoy!