Whats the fastest or most efficient way to lose weight at the gym?

I have been wanting to lose weight for a while now, but never found any real inspiration to go out and lose it. Now I’ve joined a gym and got a membership. Because I’m paying for it, its more of an obligation now just like going to work, paying the bills, or feeding the animals.

My question is what should I do there to lose weight the fastest? I know I should alternate the type of workout I do everyday, but are there certian ones I should be doing more of, and what should I avoid doing?

Thank you