And don't mistake thirst for hunger. Drinking a few cups of water before, during, and after working out can help avoid such confusion.
"So many people go to the gym and do the exact same thing all the time," Callahan said. "But the more you do something, the more efficient the body gets at doing it."
The net result is that it takes less work, less exertion to do the same old exercise and the benefit from it decreases slightly.
In addition, a stagnant routine can get boring, making people more likely to stop exercising. Studies have shown that varying exercise routines help people to stay engaged and makes them more likely to continue being active.
And working the same muscle groups all the time while ignoring the rest can cause an overuse injury.
"The benefits of exercise are largely specific to the muscle groups you use," Franklin said.
Incorporating aerobics, stretching, resistance, games and activities like yard work into a routine can increase your physical abilities and bring the most long-term health benefits.
"Do what you think is fun. And do something that's going to hit all of your muscles," Carey said.
There is a multitude of ways to look and feel better, and chances are that those who are exercising want the benefits of all of them. Setting a goal could be the best way to get there, but it is often the step that people skip in favor of jumping right on the treadmill.
"It's important for people to set realistic goals," Franklin said. "If they're 30 pounds overweight ... they're not going to reverse that in two to three weeks."
But setting the right goals can be tricky -- too high can spell failure and deter people from continuing their regime. Too low, and one has no sense of accomplishment.
"It's best to set small goals. Once you reach those goals, set higher small goals," Carey said, such as scoping out a nice gym, signing up for membership and trying to go twice a week. "A sense of accomplishment is encouragement to set more goals. It makes you feel like you really want to work for it more."
Callahan urged people to consider goals that are not related to appearance.
"You want to lose weight, but why?" Callahan said. "There's a million things it will do for you rather than making your thighs thinner," including reducing stress, the risk of high blood pressure or diabetes, and improved sleep and sex life.
"You've got to think, I'm doing this as an investment in me," Callahan said, pointing out that studies show that people who exercise with health goals in mind report more satisfaction with their fitness routine.
Spotting someone is to assist them with an exercise where necessary if that person needs help. People typically spot each other when doing activities that involve a lot of weight, particularly when that weight is being lifted above the body, such as during a chest press.
Having a spotter can be very helpful -- and a good safety measure -- but many people don't know how to spot correctly.
"[People] think they need to spot everything," Carey said. "But it can be a distraction for a lifter, especially if it's not necessary."
Rather than focusing on the person exercising to see when and where they might need help, spotters could get distracted by a conversation or by something else going on in the gym and neglect their friend.