Plan Your Tote
Before you buy fabric and pattern or any notions, think about what you want from a laptop tote. Decide if you want separate compartments for power cords, a mouse and mousepad, and any peripherals you routinely carry with you. Decide if you want a zippered top or a single snap, with or without a flap closure. Think about if you want the handles to be wide or narrow, long or short, of webbing or of the same fabric as the rest of the tote. Remember, also, that you'll want the handles to be very strong and very securely attached to the tote. Consider double-stitching or reinforcing the strap attachment with a D ring.
Finally, decide what material you'll use: Leather, upholstery fabric, vinyl, canvas and heavy broadcloth are good choices, as they're naturally sturdy. You'll want your tote to stand up on its own, so a separate, rectangular bottom gusset piece is a good idea. The combination of fabric, padding and lining together should result in a stiff-sided tote: This will also make it easier to slide the laptop into the tote.
Sketch out your ideal tote, noting the required width, depth and length needed to allow your laptop to slide easily into the tote.
If you're an experienced seamstress, you'll likely be able to design your own pattern. However, commercial pattern companies offer many tote patterns. Use your sketch to help you choose the pattern that most closely matches your needs.
Materials and Findings
Although you can find fabrics, snaps, zippers and standard sewing supplies at a traditional retail fabric store, consider shopping at a wholesale fabric warehouse as well. Fabric warehouses have enormous and varied inventory. You'll find specialty fabrics, zippers, fastenings, trims and purse and tote hardware purchased from manufacturers overstock: You may well find trim and yardage of the very fabrics used in commercial totes. As a final bonus, prices are deeply discounted at fabric warehouses: You might be able to buy a luxury tapestry fabric or leather for about the same price you'd pay for a heavy broadcloth at a retail fabric store.
Construction
Double stitch each seam, with the second row of stitching 1/8 to 1/4 parallel to the first. Even if the pattern doesn't specify it, add a slippery fabric lining to the tote so that the computer will slide in with ease, and stitch the lining to the outer shell of the tote at the bottom so that the lining doesn't sag and fold. If your design calls for a zipper, use a heavy-duty nylon zipper instead of a metal one to avoid scratching the laptop.