Sataria, here's whats working for me so far, a fitness newbie, and maybe it could work for you:
Find a gym-like program that works according to a hard-bound schedule, where you can anticipate seeing the same attendees & trainers every day. For me, it adds in a little bit of extra social pressure to keep attending. And since there's people around me doing the same thing I am, I'm less likely to want to slack, and will push harder. Furthermore, it took a bit of money to sign up, and I don't want to waste my sessions... so I don't skip em.
When I try to do stuff like running on my own time, well... I just don't. Because I honestly hate this whole fitness thing, even though I want it's benefits. So adding that extra bit of social and financial pressure to keep going really REALLY made the difference for me. If not for that, I'm certain that I wouldn't be doing this at all. So that's a viewpoint to consider, might be valuable if you're a little bit like me.
I highly suggest searching your area for a gym that specializes in the Crossfit
program. Their methods give the fastest, and most useful, results. It seems as if it's basically for athletes and people who are already fit, but that's not true. The classes I attend
are about half men, half women, about 1/3 of them look like they're 45+, and about a third of the people are out of shape like me. It's absolutely for everyone.
So do give it a look, I really feel its the best way to go if you're thinking about joining a gym.