Your first class should be machine basics, not a project
The most common beginner mistake is signing up for a tote bag or pillowcase class before knowing how to wind a bobbin. Project classes assume you can thread the machine, change a needle, and hold a seam allowance, and if you cannot, you will spend the session waiting for the teacher to come rescue you while everyone else sews. Look for a class literally called machine basics, learn your machine, or sewing 101. A good one has you stitch on paper or scrap fabric first, straight lines and then curves, before you touch a real project. You will cover threading, bobbin winding, top tension, stitch length and width, backstitching, and why the needle should be replaced far more often than you think. Once that is in your hands, a drawstring bag or pillowcase is a fine first project and a zippered pouch is a good second one. Skip the full garment until you have a few hours on a machine; a class that promises a finished dress in three hours to total beginners is either overpromising or doing most of the work for you. If you already own a machine, bring it, because learning on the machine you will actually use at home is the whole point.
One-off workshops versus a series, and when each is worth it
A one-off workshop is two or three hours and produces one thing: a tote, a pouch, hemmed jeans, a table runner. It is the right format for finding out whether you enjoy sewing at all, and for picking up a single skill like installing an invisible zipper. A series runs four to eight weekly sessions and is where actual skill gets built, because you get homework, you make mistakes at home, and you bring them back to be fixed. Garment construction, learn-to-quilt, and beginner sewing curricula almost always work better as a series. Many quilt shops run block-of-the-month programs where you pick up or buy a new block kit each month and often meet as a group, which is a series in disguise and a cheap way to stay accountable. Open sew nights are the best value in the building: you pay a small fee or nothing, bring your own project, and a teacher floats around answering questions. Retreats are multi-day events, often at a lodge or camp, with long uninterrupted sewing hours and a teacher on hand; they cost real money but people finish projects that have sat in a closet for years. Kids and teen camps are often a week of half days in summer, though formats vary by shop. For any of these, ask about the student-to-teacher ratio before paying, because a room full of beginners with one instructor means idle machines and frustrated kids.
The supply list is where people show up wrong
Every class posts a list of what is included and what you bring, and the list is not a suggestion. If it says quilting cotton, do not bring a slippery rayon challis because it was pretty; you will fight it the whole class and learn nothing about the technique being taught. If it says prewash, prewash. Included items usually mean the pattern or handout, sometimes a fabric kit, and use of a classroom machine if the shop has them. Bring items typically mean fabric, thread, fabric shears, a seam ripper, pins, and a marking tool. Buy decent thread, something like Gutermann Sew-All or Mettler Metrosene all-purpose polyester, because bargain thread sheds lint and breaks under tension and you will blame the machine. For quilting classes you need a rotary cutter, a cutting mat, and an acrylic ruler; an Olfa or similar 45 mm cutter and a 6 by 24 inch ruler are the standard starting set. Clover Wonder Clips beat pins on bulky seams and bag bottoms. Pilot FriXion pens are popular for marking because the ink disappears with heat, but know that Pilot did not design them for fabric, the marks can come back below freezing and can leave a faint ghost line on some fabrics, so test on a scrap and do not use them on anything that matters. If you are bringing your own machine, pack the foot pedal, power cord, manual, and the accessory box with all the feet. Someone in every class forgets the pedal. Shops often discount class supplies on the day, so ask before you buy everything ahead of time.
You do not need your own machine yet, and a class is the cheapest test drive
Many shops with a classroom keep loaner machines, and machine dealers in particular want you on theirs, because the classroom is really a showroom. Use that. Two hours on a mid-range Janome, Bernina, Baby Lock, Brother, Juki, Pfaff, or Husqvarna Viking will teach you more about what you actually want than a month of reading reviews. Pay attention to how the machine feeds over a thick seam, whether it has needle up and down, a speed slider, and a thread cutter, how loud it is, and how the buttonhole comes out. Then compare that to the light plastic machine you were about to buy online. When you do buy from a dealer, ask what classes come with it; many dealers include free owner classes, sometimes called mastery classes, that walk you through every feature of the machine you just bought, and a machine you understand is a machine that gets used instead of stored. Do not buy on class day because the teacher was nice, but do ask what a floor model goes for. If you are bringing your own machine to class, have it serviced first if it has been sitting. A machine that has not been cleaned or serviced in a decade will run rough, throw its tension off, and skip stitches, and the teacher will spend your class time on the machine instead of on you.
What separates a good teacher from someone who just sews well
Plenty of excellent sewists are poor teachers. The good ones demonstrate a step, then step back and let you do it, then walk the room watching hands instead of talking at the projector. They explain why: why grainline matters, why you press every seam before crossing it, why a 5/8 inch seam allowance is different from a quarter inch. They can teach on a machine that is not the brand they own. They will tell you to unpick a seam and show you how to do it without making you feel like an idiot. Warning signs are a teacher who sews your project for you when you fall behind, a class that runs long with nobody finishing, no written handout to take home, and a classroom with no irons. A sewing room without a pressing station is a red flag, because pressing is half of sewing and a teacher who skips it is teaching bad habits. Ask about the teacher's background, since garment sewing, quilting, and machine embroidery are genuinely different disciplines and a quilter teaching a fitted bodice is guessing. Read reviews for the teacher's name specifically rather than the shop, because shops rotate instructors and one great teacher can carry a mediocre store. Small classes matter more than a fancy classroom; six students with one teacher beats fifteen with two.