Programs like Starting Strength and the New Rules series are a great place to start. I've done New Rules for Women and loved it, but I think I'd recommend that you start with one of the newer books--probably the New Rules of Lifting for Life. That is geared towards gaining strength and fat burning, so it is pretty good for people in our situation. I've never read Starting Strength but it is a benchmark place to start. The books are helpful because they help you to understand what you are doing and why you are doing it.
If you didn't want to start with a program and just wanted to try things out for yourself for starters, I'd recommend putting together a basic compound lift program for yourself. You could either do a full body workout 3 times per week, or you could alternate upper and lower body days more often. It depends what you want to do, how often you want to go to the gym, and how long you want to stay there.
This is what I usually recommend (and what I do myself when I'm getting back into things and not doing a program). The internet is filled with videos that help you to do these exercises correctly. I'd probably start with two or three sets of 10 for each exercise. During the first couple of workouts, you'd want to focus on getting your form right (ask trainers at the gym, if you're not sure). After that, the goal is to lift HEAVY: you want to be close to exhausted at the end of every set. And you should be striving to increase your weight on each exercise every time you workout. (You won't be able to do that, probably, but that is your goal). Take 30-60 seconds to rest between sets.
Lower body:
These exercises work all the big muscle groups in your lower body. There are millions of variations, but this is where to start.
Squats Begin with
goblet squats and build up to
barbell back squats.
Deadlifts: Deadlifts are an absolutely brilliant and critical exercise, but it is really important to do them properly. Before you start, watch lots of videos and make sure you get the form right. If you want to start with a baby step, I'd do
Romanian Deadlifts to begin with, and then move onto regular deadlifts once you get more comfortable.
Lunges/step ups: You can alternate these or do lunges for a few weeks and then do step ups. Or whatever. Variety is good and both of these are great exercises that work your quads and glutes slightly differently.
Planks: the new research shows that crunches are bad for your spine. Planks are better. Start by holding for 30 seconds and work your way up to 90 seconds.
Upper Body.
The simplest and most effective way to work your upper body is to do big compound lifts (that means lifts that use LOTS of muscles working together rather than just one little muscle working alone--such as bicep curls or tricep extensions. Life is too short for those unless you're a body builder.)
The way to think about this is that you want to do a PUSH and a PULL and you want to do each of those HORIZONTALLY and VERTICALLY. There are LOTS of variations you can do, but here's what it would look like:
Horizontal Push: the
push up is the benchmark exercise for this. If you can't do a regular push up on the floor, do them on an incline. Any old piece of equipment that you can push up against will work. Walls work too, if you're starting from scratch. An alternative to the push up is an
incline chest press, with dumbbells. Those are a bit friendlier to start with.
Horizontal Pull:
Rows. There are millions of variations. You can do the
seated row on gym equipment, you can do a
barbell row, you can do a
1 point row with the help of a bench (my favorite), etc, etc. Lots of variations. Play around and find what you like. It's important to do these with a heavy weight so that you engage your back muscles rather than just your arms.
Vertical Pull:
Latt pulldowns. You do these on a machine, usually located with the free weights rather than in the general machine section of the gym.
Vertical Push:
Military/dumbbell press, standing up. Awesome exercise.
That's a pretty basic but effective place to start. Warming up is good--I used to run for 10 minutes but the new NROL books have you doing some fun dynamic warm ups instead. (I love the squat-to-stand exercise).
With whatever energy you have left, you do 10-20 minutes of HIIT to shake up your metabolism and burn some fat--this can be on the treadmill or elliptical or something else. My new favorite are kettlebell swings: 20 seconds of fast, hard swinging; 40 seconds of rest.
Hope that helps. Feel free to ask questions.