Trainers see just about everything when it comes to bad gym behavior, from moves that put muscles and joints at risk to careless habits that endanger the health of others (or simply annoy them).

SafeBee asked several trainers about the most common mistakes they see, and for their advice on how to stay injury — and embarrassment — free at the gym.

Mistake #1: Engaging in boot-camp madness

You’re pumped you made a commitment to get fit, and you can’t wait to crush your first workout. But do too much too soon, and at the very least you’ll be very sore. “Two-a-days and high-intensity boot camps are for sports and the military, not for building a solid base of a healthy life and body,” says Dallas-area fitness trainer and health coach Clint Fuqua, NASM-CPT. “Simply surviving a workout is not the way to increase health for the long term and will normally leave you on injury reserve, getting depressed and fat on the couch.”

Mistake #2: Diving in without warming up

You want to get in and out of the gym in the most efficient way possible. But don’t just go full-swing into your kettlebell swings or strength circuit or sprint intervals without first priming your muscles for the demands you’ll be making on them. “I rarely see anyone do anything related to a warm-up: no foam rolling, no stretching, let alone a dynamic warm-up,” says Henry Halse, CSCS, ACSM-CPT, a trainer in Philadelphia. Spending a few minutes doing arm circles, leg swings, and a few warm-up squats, for example, can save you pain and possible injury later.

Related: Injury-Proof Your Exercise Resolution

Mistake #3: Believing the calorie burn on the screen

Cardio machines display all sorts of numbers: distance traveled, speed, heart rate. And every gym-goer’s fave: calorie burn. Sad news: This number could be inflated — by up to 42 percent, according to one report.

Mistake #4: Sticking to all cardio, all the time

Access to treadmills and ellipticals may have been your impetus for joining the gym, but don’t get cardio tunnel vision. “If you do the same aerobic workout every day, your body will adapt and you won’t see the changes you want,” says Kate Vidulich, ACSM-CPT and the founder of FatLossAccelerators.com. Mixing up your routine is essential to keeping your muscles — and you — from getting bored.

Be sure to also lift weights or do some other form of resistance training, especially if you want to maximize your calorie burn even after you leave the gym (this is known as the after-burn effect). “Strength training increases basal metabolic rate (BMR) meaning you use more calories to live,” says San Antonio-based personal trainer Brandon Mancine, NASM-CPT.

Related: How to Stay Germ-Free at the Gym

Mistake #5: Lifting weights that are too light

“Women in particular tend to underestimate their lifting ability, and therefore never reach their full training potential,” says Vidulich. “Why? They don’t want big muscles. But lifting light weights for a billion reps won’t create the intensity required to get any noticeable results.” How do you know that you’re properly loaded? If you can do 10 reps and feel like you could do easily do five or more additional ones, you gotta go up. Ideally, you should have just enough gas to maybe churn out two or three more.

Mistake #6: Lifting weights that are too heavy

Overloading yourself is a bad idea, too, and a recipe for injury. “Not everyone has the biomechanical or neuromuscular structure to control heavy squats or bench pressing, so don't put square pegs in round holes,” says Marc Megna, CSCS, an NFL player turned strength coach and co-founder of Miami’s Anatomy at 1220. “There are regressions, progressions, and alternatives for every exercise. The goal of every training session should be to be able to perform the next training session.” If you’re not sure how to choose the right weight or exercise for you, ask a trainer.

Related: Can't Get Into the Exercise Habit? Try this Trick

Mistake #7: Ignoring your form

How you perform an exercise is as important to your wellbeing as getting to the gym in the first place. Bad posture, incorrect or incomplete range of motion, and compensating with one muscle when you’re looking to work another — all of these mistakes not only sacrifice the quality of your workout but increase your risk of injury. “For strength training, I tell my clients: Learn the movement, then challenge the movement,” says Mancine. This often means literally going through the motions with no weight at first.

Mistake #8: Zoning out on cardio machines

Bad form can happen on cardio machines, too. It’s easy to just let the machine chug along and not watch your posture, or worse. “I can't tell you how often I see people on stepmills looking to work legs and butt, hunched over in a posture that makes it impossible to fire their glutes fully if at all,” Mancine says. Never hold on to a cardio machine unless it’s designed for you to do so (like ellipticals with moving handles), and look straight ahead — not up at a TV or down at your magazine — to avoid neck troubles.

Mistake #9: Not consulting a pro

For some reason, people are unlikely to ask for help or advice from the trainers at the gym. (Educated guess: They’re worried she’ll try to hard-sell them to buy sessions.) Instead, they watch other gym-goers to get ideas, or chat with the lifter on the bench next to them. “Commercial gyms are also universities of ‘broscience,’” Halse says. “When someone has a question, everyone instantly becomes a fitness/nutrition/rehab expert and gives their two cents — it makes me cringe.” First, the advice might be flat-out wrong, and second, what might work for one person’s body or goals may not work for another’s. Many gyms offer complimentary training sessions when you sign up. Take advantage. Ask lots of questions. (And have your “thanks but no thanks” speech ready for the sales portion, if need be.)

Related: How to Avoid a Treadmill Accident

Mistake #10: Not dressing for success

This one seems like a no-brainer, but it happens. “Booty shorts and flip-flops both have their place and it's not in the gym,” Fuqua says. “Leave the beachwear in the bag and come to the gym dressed to train so you can look great at the beach later.” That means, ideally, wearing clothing made of performance material that wicks sweat away from your skin and dries quickly, and choosing appropriate shoes for your activity.

Mistake #11: Being a slob

Do your part to keep this shared space tidy. Follow the rule kids are taught in kindergarten: If you use it, put it away. And that’s not all. “I get it — working out is sweaty business. But not wiping down the equipment or cleaning up after yourself really gets up my nose,” says Vidulich. “Please use a towel!” Wiping down surfaces before and after you touch them is also a good way to avoid getting sick at the gym.

Amy Roberts is a certified personal trainer. She writes about fitness, health and a variety of other topics for many well-known publications.