I have always liked running most of any exercise but was never any good at sticking at anything.
I started Couch to 5K almost 3 years ago - I ran regularly for 6 months until I became pregnant, stopped for a year but started again when dd2 was 4 months old and have been running ever since (about 16 months).
What has helped ?
A good starting programme like nocake says. Couch to 5K is good as you cna download podcasts which make it very easy to follow. Join a thread on here for encouragement/tips etc. I think there is usually a couch to 5K one going.
Getting into a 3x a week habit. Forcing yourself out until it becomes the norm. Ideal if you can set yourself the same time each week. I have to do 2 sessions in the gym a week as dh isn't around much and I need the creche for dd2. I have the same slots each week so it is part of my routine. I then usually do a long run early saturday or sunday morning.
Really wanting to reach a goal - book a 'proper' 5K in for say 3/4 months time so you have time to do a programme and then be comfortable with the distance. Then you have a reason to do it. I did a 5K first time round and then just did a 10K and each 6 months am going to book a longer and longer run until I reach the marathon (gulp).
Also, once you start losing weight/getting fitter/ gain energy that will help keep the momentum up. I lost a fair bit of weight first time round which is what inspired me to get back to it. I know it keeps the weight down and I'm no good at dieting.
Good luck ! You can do it. And for more inspiration think of my mother - she said she couldnt' run, used to cheat at cross country. Decided she needed to lose weight as she had some colestrol issues so started couch to 5K 9 months or so ago and still runs 3 x week and is up to about 6.5K now. She's 66.