I taught 3rd grade for 13 years. These are the things I did:
*Check with team on pacing guide and make sure all resources/curriculum are available.
*Plan 1st 2 weeks of lessons/procedure practice - and make any copies for them
*Decide on furniture placement (your desk, their desks/tables, small group area, library,....)
*Decide on bulletin boards in classroom (#1 with information: "what to do when you arrive", "what to do when you pack-up", "weekly skills"), (#2 for A.R. progress)
*Hallway bulletin board - put laminated cardstock then glue clothespins for each student (to show their work).
*Create first week newsletter
*Create letter to parents introducing yourself.
*Sharpen pencils
*Make word search with kids' names (when you know them) to have on desk for 1st day.
*Create "me bag" as model, then have theirs ready for 1st day.
*3m clip on front door and hang something with your name (going along with a theme if you have it)
*Create "Information sheet" to give procedures/rules for each child.
*Place for birthdays
*Transportation list ready for the first day.
*Camera or iPad out to take 1st day pictures
*File for each student to add papers as you get them
*Sharpies out to label personal items for their desks/cubbies
*Tubs labeled to put any community supplies
*Plan for 1st read aloud (I like
The World According to Humphrey to start, with a stuffed Humphrey sitting by me

)
*Clipboard with bus numbers/car riders so you can add their names to it as you know. Then you take the clipboard with you in the afternoon (depending on how your school does it).
*Buy colored paper for any newsletter, introduction letter, etc... so it's ready when you can make copies.
Some of those things you can do from home ahead of time (introduction letter, etc...), so I would advise that. Then you can make the copies when the copier is free once you get there. That was always hard to squeeze in, so do that as soon as the copier doesn't have someone! Have your stack of papers that need to be copied ready.