1-Mailing labels. I HATE taking time out of the submission process to print address and return address labels. The printer usually eats something or the labels are out of alignment and suddenly, it's time to go pick up the kids. I am printing return address labels and SASEs now. I will have a stash available and only need to print out the mailing label when I am ready to submit.
2-Postage. Did you know you can purchase $1 stamps? How about 5 cent stamps? Those yellow envelopes that hold your clips and queries cost (currently) $1.05 to mail...unless you go over 2 ounces. Save trips to the Post Office and buy your stamps before you need them. Also, consider a scale so that your postage is correct every time. (USPS online has current rates for postage).
3-Supplies. Did the kids use your stapler for summer crafts? Where is that red pen and did I take my essay journal to the beach or to my parent's house? Check printer ink, your paper supply and batteries in your recording devices, etc. Get your supplies in place so that everything is within arms reach.
Go to the office supply store today. Don't wait. Can you be ready on the first day of school?