GPS systems have fallen substantially in price, and can ensure you never get completely lost by adjusting to your current position. However, in the heat of the moment you can still make a wrong turn even with a GPS (which right turn is it actually talking about?), so plan your route a little bit before hand either with your GPS, online, or with a good old fashioned roadmap.
There are other aspects of trip planning besides just getting there the fastest way possible and avoiding getting lost. Thinking ahead to avoid rush hour and other traffic can save time, frustration, gas, and wear on your car. Sharing a ride is a way to cut your emissions in half (or more), while accessing the speedy car pool lane for free.
You can also plan ahead to combine your trips (errands and picking up the kids, for example). Combining trips can mean driving fewer miles overall and a warm engine functioning at maximum efficiency.
Excess cargo weighs down you car, making it work harder and burn more fuel. So, if you don't need it on this trip, leave it behind.
Finally, by keeping track of your fuel economy-recording how far you drive and how much gas you consume-you will be able to spot problems as they emerge and get them taken care of before they progress.