A friend recently asked me to help him get started with weight lifting. He trains regularly on a treadmill, but has never done strength training. My first impulse was to invite him to follow me around while I showed him various exercises, but, on second thought, he needs to answer two questions first.
Which muscle groups do you want to strengthen?
These pictures show the main muscle groups. Don't worry about the formal names -- "abs" will do for "rectus abdominus" -- but set some priorities. Do you want to strengthen your legs? Chest? Arms? It would be nice to say "all of the above," but you probably don't want to spend as many hours a week in the gym as the folks in these pictures.
These pictures were taken from Bodybuilding.com, where you can see them with links to diagrams of each muscle. You should go there and familiarize yourself with the muscle illustrations, because, when you do an exercise, you need to be aware of which muscle you are training, and focus on isolating it.
How many days per week will you work out and how much time will you spend each day?
When I worked out at a gym that was far from my house, I went three days a week, and worked my entire body each time. Now that I am working out near my home, I go 5 or 6 days per week, and do different body parts on alternate days. For example, you might do arms and chest one day and legs the other.
If you choose to go only two or three days a week, you will want to spend enough time to do your entire workout. If you do that, alternate body parts, for example biceps and quadriceps, within the workout.
I've never experimented with two-day per week workouts, but I just found one study indicating that it might be as effective to do a long workout two days a week as doing a short workout three days a week. (The study was of relatively young men and (mostly) women). It would be interesting to find more research on the topic and to do some personal experimentation. I doubt that one day per week would do much more than make you sore.
After you get used to the exercises you like for each muscle group, you will see how long it takes and you can adjust your workout accordingly. And, if you get hooked, you can increase the time you spend in the gym.
I've got some good news regarding time -- the time you spend in the gym pays dividends. Your energy and endurance will increase, so you will get more done during your time outside the gym. You can also use a portable audio player to listen to music or words while working out. I listen to a mix of professional conference presentations and NPR programs. Others may prefer books on tape or music. Regardless, it is making dual use of your time in the gym.