There is a variety of proven weight training programs out there and I believe it’s just a matter of finding one you’re gonna believe in and sticking to it religiously. Go through with the program you picked, do not abandon it after few unsuccessful attempts to follow it, or after a short period of time, frustrated that you don’t see any results. It just so happened that I was inspired by a person I’ve met, who showed me his before and after the “Body For Life” pictures and that was what “sold it” to me. I went online, bought the book and dedicated myself to following it for a couple of months. One I saw first results - it motivated me to stick with the program more than anything else could have. But enough about me, let me share with you the basics of the program.

The “Body for Life” program is actually quite simple. There are only few rules you need to follow:
 

Rule #1 - Exercise hard, rest well. Alternate your training days. Remember, your muscles grow when you rest, not when you exercise! When you stress your muscles, you pretty much break its tissue, forcing them to re-grow stronger and bigger. That’s the idea. Therefore, stick to the following schedule:

Day 1 - Upper body, Day 2 - Cardio, Day 3 - Lower body, Day 4 - Cardio, Day 5 - start from the beginning, e.g. repeat Day1, etc.
 

Rule #2 - Perform 6 sets to exercise each muscle group. For upper body - pick two different exercises for each muscle, and do 4 sets of the 1st exercise you picked and then 2 sets of the second exercise you picked.

Weights: pick a weight with which you can comfortably do 12 reps, without killing yourself, but hard enough that you have to “work for it”. Done?
Suppose you picked 15lbs. Now here is how you do the weights during these 6 sets:

1st set: 12 reps with 15 lbs using exercise 1
- rest 1 min -
2nd set: 10 reps with 20 lbs using exercise 1
- rest 1 min -
3rd set: 8 reps with 25 lbs using exercise 1
- rest 1 min -
4th set: 6 reps with 30 lbs using exercise 1
- rest 2 mins -
5th set: 12 reps with 20 lbs using exercise 2
6th set: 12 reps with 15 lbs using exercise 2

The 4th set (6 reps) should be the toughest - you should be hitting 100% trying to push that 6th repetition… there should be absolutely no way you could do the 7th. If that’s not the case, if you feel that you can go for more - next time start heavier. If you can’t complete any of the sets - next time start lighter.
 

Rule #3 - Always plan your training before hand.

And at the beginning, it might be a good idea to record all your weightlifting exercised in a journal indicating the exercise selected and weight lifted. But in just few sessions you’ll start remembering it…