How can I begin a weight-training program?

First off you want to know what your goals are first.  Once you have decided weather you want to lose weight, increase muscle mass, improve balance and endurance or just a variety of them.  Then I would suggest to meet with a certified personal trainer to map out what you should be doing for your resistance training, cardiovascular training and meal planning.  If you don't have access to one because maybe you are working out from home best rule of thumb is start out light and work your way up from there.  A great start is 2-3 sets of about 10-15 repetitions.  Also listen to your body as well.  Your body will tell you if it is too much or such movements are painful for you.

If you would like to start a weight training program for the first time, I recommend that you find a qualified profesional to help you out.  They will be able to assess and determine which exercises you should begin with and how much weight to start with.  Also, I have found it to be very beneficial to have someone watch me perform the exercise because they can critique my form until I have the body awareness to correct myself on form.  Form is very important when engaging in a strength training program.

Here are some basic rules to follow while weight training:

• Generally, you should use as much weight as you can lift 10-15 times in one "set." (A "set" is one series of repetitions before you stop to rest.) For a more "aerobic" workout, use lighter weights and higher reps, perhaps 15-20 per set. And be sure to warm up thoroughly before your workout. For a "warm-up" set, use much less weight and do many more reps, perhaps 25-30. For a particular exercise, you might do two or three sets, or even more. Rest between sets for 40 seconds to 2 minutes. Less rest than that won't be sufficient, and with a longer rest, there's a risk your muscles could cool off and tighten, making them prone to injury on the next set. 
• Add weights only when you can complete 10 reps comfortably on your final "set" of any particular exercise. Another way to increase the load is to increase sets, or the number of reps in each set. 
• Be consistent. Any strength training is going to help, but lifting only occasionally will make you sore, without doing much to help you build strength. One day a week will help. Two days a week is better, and you'll see some gains. Ideal is three days a week, or more provided you're getting adequate rest.

In the very beginning, start with one set using low weights and high reps for each body part. For most exercises, after a couple weeks, or as you begin to feel stronger and more confident, add a set. After a couple more weeks, add a third. 

If you are new to weight-training or new to exercise as a whole then you need to be sure start simple and start smart.  Prior to any form of exercise you should feel comfortable what you are doing.  If you are unsure of how to perform proper form with exercise then it would be best to seek guidance of a certified professional.  No one enjoys being discouraged and if you are doing exercises incorrectly then you may be discouraged if you are not seeing results and the possibly for injury is much higher.  A great way to start a program, if not seeking professional advice, would be to take advantage of strength training equipment in your fitness center.  This equipment will assist in aligning your body properly and should help to avoid injury.  Start there and then when you get comfortable, more onto cable machines and free weights!

Beginning a weight-training program is a task many take on without taking the proper steps to ensure they are physically ready. First and foremost, always consult your physician before beginning any exercise regimen. Once you have clearance you should seek the advice of a professional for a functional movement assessment to ensure that you do not have any muscle imbalances or improper movement patterns that may be exacerbated by beginning a strength training program prior to a corrective exercise program. After the above steps are complete you are ready to begin.

You will want to start out with low intensities (low weight/body weight) and slowly build yourself up to higher intensities over time. Keep in mind that this will be based on your overall goal. Starting out with exercises that encompass the entire body (lunge w/rotation, squat to overhead press, push-ups, etc.) will help you develop strength and stability for more intense exercises later in your program. Remember, beginning a strength training program does not have to start with weights, you have a whole body that can be used for resistance exercises in the home to build a nice foundation to add to.