If you are just beginning to strength train or weight train, here are some pointers to remember: When you train one muscle or muscle group, you need to also train its opposing group. For example, when you train chest, you MUST train back. It doesn't necessarily need to be on the same day, but it does need to be trained in balance with its opposition. Some people even need a few extra back sets to chest sets, to correct rounded shoulders.
Start with the largest muscles or muscle groups first. If you are doing an upper body day, begin with back, then chest, making your way down to the delts, triceps and biceps. This allows all of these smaller muscles to become well warmed up, and used to assist the larger muscle group, so that you can really tackle them in isolation towards the end of your workout.
Always do a warm-up before your strength training. It doesn't have to be on a piece of cardio equipment. You can also do a couple of very light sets of the exercise you intend to undergo - the point is that you get blood pumping through the muscles you will be working, and use as many muscles as possible. Everybody has different needs in terms of the proper warm-up time, but 3-5 minutes is normally sufficient, depending on the activity.
Don't hang around between sets. Honestly, if overall fitness is your goal, involve your heart rate. Keep it moving. Grab a drink between sets to stay hydrated and give your muscles a quick break, but don't lounge around. You are training your body to be more fit, to be stronger, to move better, right? So why would you sit around in the process? You want your heart and your muscles to be equally fit, so that one does not give out before the other in any given activity.
Fuel and re-fuel for your workout. I've found that most of my clients are comfortable eating a small meal (about 200-300 calories) about 45 minutes before their workout. A small bowl of cereal is excellent, or a yogurt and piece of fruit (plain yogurt is best). Basically you want to be a bit more on the carb side before your workout, and then re-fuel with a bit more protein afterwards. Remember to include all three macronutrients (carbs, protein and fat) each time you eat for optimal energy - but definitely get some good quality protein in within 30 minutes of finishing your workout. Strength training is the muscle breakdown part of the equation, and proper nutrition and sleep ensure the muscles repair themselves optimally. So, a hard boiled egg, a yogurt and some blueberries is sufficient, for example.
Obviously program design is incredibly complex. If you're feeling a bit lost, hire a trainer. A trainer will take into consideration all of your anatomical imablances, work on your strong points, develop your weaker points, pick up the heart conditioning, structure everything so particularly to give you the very most bang for your buck. There is a lot to know, and don't underestimate how calculated a specific program can be! Everything is in place with good reason.
And remember if you have questions... put me to work! Send 'em over. Happy lifting.