Engaging in regular exercise is one of the smartest investments anyone can make, especially if you’re a single parent who needs the energy to keep up with her kids. And when we say “investment” we’re talking about time and effort, not money. To show you what we mean, here are several free (or almost free) ways to get in shape. Use these tips to give you the guidance and motivation you need to achieve your fitness goals. Stick With the Basics  TV programs love to show images of people with big arms and sculpted abs. The purpose behind most of these promos is to sell you some kind of overpriced product, usually with the promise that it will turn you into a superhero. Sadly, the real world never works that way. Most home fitness machines end up as overpriced coat hangers or yard sale merchandise. So skip the gadgets and start with these four classic routines instead: Pushups. This one exercise can do you more good than all the fitness products on the market. It strengthens the arms, shoulders, chest, abs, and even the legs. Plus, it costs you nothing. You need only a small amount of space and the motivation to improve yourself. And don’t beat yourself up if you can’t do a standard push-up right away. There’s no shame in starting at the intermediate level by bending your knees. Soon you’ll be pumping them out with the best of ’em. Situps or leg raises. This exercise will bulk you up without draining your wallet. Some people have trouble doing sit-ups because of neck or back issues. If that sounds like you, then leg raises are a great alternative, according to the fitness experts at the New York Times. Squats/deep knee bends. Not only will this exercise give your…