Strength training. Am I losing my time?

May start with a dumbbell in the 10-15 lb range if you're new to it. If you aren't tired at all after one set then switch to a heavier one

It sounds like you've never done strength training. Most women and many men don't start with 50 pound dumbbells or a high setting on a machine. You have to work your way up. Your goals also matter. I would book an appointment or two with a trainer or buy a good book. Anytime you're working hard with good form is beneficial, regardless of the weight.

heavy lifting is just that...Lift what feels heavy to you! You should start at something that is farely challenging at about 8-10 reps x3 sets and the last few of the last set should be rather difficult. There isn't a set # to start at for every person, just pick something that feels fairy heavy and pump it. lol. I use a combination of machines, barbells and dumbbells really depending on my mood. hehe

OK, great, that's exactly what I've been doing for the past 2 weeks.
So I don't have to follow those programs they're talking about, like Stronglifts 5x5, New Rules of Heavy Lifting for Women, etc.?
I was afraid, because frankly, I'm have a pretty weak upper body, he he he

From what I've heard, Stronglifts is a good program. I'm sure it assumes that a new exerciser will start with the weights she can handle,no matter how light. To coin a phrase, you have to walk before you can run.

"My goal in fitness, for the moment, is to lose weight without losing muscle mass."

This is a laudable goal but very difficult to achieve. In my own case, I dropped from 214 lbs to near 160 lbs over the course of six months. I trained consistently during those months using mostly free weights. Over the course of those six months I ended up taking off between 20-30% of the amount of weight I could lift prior to losing weight; which translates to loss of muscle.

You will find, that due to a reduced caloric intake, that your energy levels during your workout will drop off quicker than if you were not dieting. It will be exceedingly difficult to lift the last few reps - you won't have the energy.

There is a whole lot to learn about lifting weights, I would get help early so you don't end up wasting your time at the gym (like I did).

"My goal in fitness, for the moment, is to lose weight without losing muscle mass."

This is a laudable goal but very difficult to achieve. In my own case, I dropped from 214 lbs to near 160 lbs over the course of six months. I trained consistently during those months using mostly free weights. Over the course of those six months I ended up taking off between 20-30% of the amount of weight I could lift prior to losing weight; which translates to loss of muscle.

You will find, that due to a reduced caloric intake, that your energy levels during your workout will drop off quicker than if you were not dieting. It will be exceedingly difficult to lift the last few reps - you won't have the energy.

There is a whole lot to learn about lifting weights, I would get help early so you don't end up wasting your time at the gym (like I did).

You lost the amount of weight you could lift? How big was your deficit? Even while losing weight I increased my strength dramatically...but I also wasn't eating only 1200 calories like a lot of people do