If you’re still driving your own car, you might need to get up to speed.

Car sharing and ride sharing have cruised into many cities around the world, especially as more people are going car-free to save money or live more environmentally friendly lifestyles. And smartphone apps are making it even easier to find available rental cars and rides.

But before you can join in a chorus of car-sharing Kumbaya, you might want some basic information.

In this week’s column, I’ll explain how car sharing and ride sharing work, how to find and access cars and how to address safety concerns. This could be helpful if you need wheels for just an hour or the day, want a ride from someone or want to offer a ride to someone. Just be prepared to pay for the convenience of quickly picking up a car and be aware of the possible awkwardness of riding with a stranger.

Wheeling in Convenience

Renting a car no longer means going to an airport or rental office to get one. You might be able to find a car a few steps from your front door. This is especially common in cities where services like Zipcar, Car2Go and Enterprise (with its Enterprise CarShare program) let users pick up or drop off cars on streets or in parking garages.

To start, you’ll need a membership with the company, which usually requires a fee, as well as some information like your driver’s license, age, moving violation history (if any) and payment information. The company will send you a membership card, which you wave over a small panel on the windshield to unlock the car and start tracking the time you began using it. Keys are inside and you’ll leave them there when you’re done. To lock the car, just swipe your card on the windshield reader again.

In the case of Zipcar and Enterprise CarShare, cars must be picked up and returned to the same spot and reservations must be made via phone, website or mobile app.

Car2Go uses a looser approach: It lets members pick up cars without a reservation (though you can make one) and it’s designed for one-way rides to anywhere within a designated Home Area. There are no time limits, though a company spokeswoman said the average person uses Car2Go for 30 minutes.

Car2Go charges according to how long you use the car — 38 cents a minute, $14 an hour or $73 a day. Zipcar offers a few plans, some that include monthly fees or annual fees, like $60 a year, as well as hourly or daily charges like $8.25 an hour and $75 a day. Each Zipcar reservation includes 180 miles a day.

Enterprise CarShare reservations include 200 miles a day and hourly or daily fees vary. Washington, D.C., starts at $5 an hour and $76 a day, depending on the model, day of the week and time of day. Enterprise is currently waiving its $25 application fee and $40 annual membership fee for the first year.

These services cover insurance and even gas, offering limited gas cards in the car for people to use and other incentives to encourage drivers to fill up the tank. On the other hand, users can be charged penalty fees for a variety of infringements like returning cars late, smoking in cars or losing car keys.

Car2Go models are easy to spot: All of the company’s cars are Smart cars painted blue and white with the Car2Go logo. The downside of this is you can’t fit much in this tiny car. Zipcar and Enterprise CarShare offer various models, including pickup trucks, so you can choose the right size car for your trip.

The Modern Chauffeur

If driving isn’t your thing, you can take advantage of several smartphone apps that bring cars and their drivers to you. Three such companies include Sidecar, Lyft and UberX, which work on the premise that average people can be drivers. (UberX differs from the more well-known Uber, which functions as an order-by-app car service using professional drivers and luxury-car options, while UberX uses a mix of regular people and pro drivers.)

These services work via smartphone apps that let passengers and drivers search for one another, follow routes on maps and even rate each other after the ride. In some cases, drivers can make money according to fees suggested by the services.

Take Sidecar, which operates in six U.S. cities. The app matches you with a driver and sends you a photo of the driver and car as they approach. The ride is tracked using GPS, which you and the driver can monitor on the app. When you arrive at your location, you can pay the driver what you think is a fair price. A suggested fee pops up on your phone’s screen, and passengers are asked to pay what they think is fair. Though you could technically opt to pay nothing at all since the services are for sharing rides, after all.

UberX riders, though, pay a base fare and a per-minute or per-mile fee, depending on rate of travel, before getting out of the car.

Finally, you can rate your driver and your driver can rate you when the ride is finished, encouraging both parties to be on their best behavior.

Of course, safety is a major concern with ride sharing. Sidecar, Lyft and UberX have $1 million liability insurance policies in place for rides. And each conducts strict background checks on its drivers to confirm proper licensing and insurance, and to guard against people with criminal offenses or driving violations. They also interview potential drivers.

If you’re tired of the expensive routine costs associated with taking care of a car, or if you want a more eco-friendly option for getting around town, car sharing and ride sharing offer a fresh twist on traditional modes of transportation.

Write to Katie at katie.boehret@wsj.com.