There are lots of reasons to exercise, such as wanting to look good, feel good, get healthy, improve stamina, improve strength or a combination of the above. Despite your reasons you need to have a constant level of motivation to be successful in achieving the results you desire. Even the folks that are in great shape and work out every day need something, or someone to motivate them.
Most people who start working out on the fly quit before they reach their goal. It's not because they didn't have a good workout regime, trainer, weight set or desired result. It's because they weren't properly motivated. You have to really sit down and come up with all of the reasons that are driving you to get to where you want to be. Some people might only have one strong reason and others might have a dozen smaller ones. The trick is to really dig deep and determine the source. "Wanting to look good" is not a strong motivational factor! You have to find the real source and come up with an image in your mind that will drive you to success. As an example, you could dig out a an old dress, shirt or pair of pants that you want to fit in to and hang them up where you will see them every single day. Maybe even hang a few items up around the house so that you simply can't forget. You want to make sure that the mental image you get from motivational item is strong enough to make you WANT to work out right that moment no matter what the excuse.
The bottom line is that the first major step to getting into an exercise program is to get motivated. Setting long term goals, buying expensive equipment or gym memberships isn't going to get you where you want to be if you don't do anything. If you just can't "get into it" then you could consider hiring a personal trainer or even getting a friend to "push" you. Just don't completely rely on the trainer as if you aren't internally motivated it will be easy to just stop paying them.
On a final note, I'm not trying to portray myself as a fitness guru as I struggle with motivation just as much as the next person.