My philosophy is to train basic and instinctively.
By basic: I mean make sure each of your work outs is built round basic freeweight exercises such as bent rows, shoulder presses, bench presses, deadlifts etc.
Keep the set scheme basic i.e. pyramid the weight up to your heaviest set. I either do 1 or 2 sets depending on how I feel at this weight or I do 1 set followed by a lighter set at approx 90% of previous weight lifted (after adequate rest 3 to 5 mins depending on how heavy it was).
Use up most of your energy on these big exercises and if you must throw in some cables or machine movements (I hardly bother), do it afterwards.
I very rarely incorporate any intensity techniques such as drop sets or forced reps, as I find I can't recover adequately from them.
Try to increase your rep range or weight used at least every 3 weeks.
Switch exercises when you plateau i.e switch bench presses for weighted dips, pull ups for pull downs etc.
Concentrate and try to get out the gym within 60 minutes.
By instinctively: I mean listen to your body. If you are tired all the time and find it hard to sleep + have loss of appetite you are probably overtraining, take some time out (at least a week - no gym), relax, sleep and eat well.
On the flip side, if your back is feeling strong and it is telling you to train it but you have already trained it 4 days earlier, then train it.
Likewise this applies to all bodyparts, just because convention suggests you shouldn't train a bodypart more than once a week unless you are a genetic freak or roided up - don't listen to convention, listen to your body. Since I stopped doing fancy drop sets, running the rack, forced reps etc I can recover a lot quicker and tend to train 1 body part TWICE a week depending on what I am concentrating on.
For example if I want to increase my bench I can train that twice a week, I find by doing it twice a week I will progress a helluva lot faster than doing a once weekly almighty mega intense session consisting of a zillion sets with drop sets and forced reps thrown in for good measure.
If I am training chest twice a week I will vary my work out i.e. low reps (2-4reps) for one session and medium to high reps (5-10reps) the other session. I will also train my other body parts only once a week during this period and when I decide to concentrate on another bodypart such as shoulders I will switch back to a once a week chest workout. This rule only applies to me but if your body can handly more bodyparts at twice a week intervals, then do it.
By example: Below is a workout schedule dated 27th July to 2nd August 2009.
* I also only train legs every two weeks. Therefore I hit the gym 3 times a week for a week and then 4 times a week next week.