Some good guidelines for sets/reps, depending on the goal of your weight routine:
4-6 sets, max reps of 6 in any set (heavy weights/low reps) - good goal is to do 6 reps on first set, then lowering reps as you add weight each set - heaviest set should be 1-2 reps, then you can have a final set using first-set weight (an you'll probably only get 4 or 5 reps).
4-6 sets, reps of 6-12 (moderate weights, medium reps) - similar lifting pattern on the sets as above, just weight adjusted so you can always do at least 6 reps, but most likely starting your first set at 10-12 reps and working from there.
Toning/full range of motion/beginning after a long break from the weight room (or just starting in the weight room for the first time):
4-6 sets, reps of 15 plus (very low weights, very high reps) - allows good, full range of motion with free weights, you can truly focus on form, great way to strengthen connective tissue (ligaments, tendons, etc.) before you move to heavier lifting.
Some rules of thumb on tissues in the body:
Each connective tissue is about twice as strong as the one before it, with muscle being the weakest and bone being the strongest. Something to think about in the weight room - you don't want to increase muscle strength/size too quickly (before the connective tissues have strengthened to take on the bigger workloads). If you increase muscle strength/size too quickly, you can damage/injure the ligaments and tendons by stressing them beyond their current capacity/strength. If you're returning to the weight room after a 3-4 month break, or if you're just starting for the first time, it is a good idea to take 2-4 weeks of low weight/very high reps to accomplish 3 things - gain correct form, develop full range of motion with each specific lift, and strengthen the connective tissue.
On sets vs. reps, the body needs at least 3 sets of a weight lift to truly gain any benefit. Best is 4-6 sets. From the 7th set on, the body does not get much bang for the buck, so the 7th and more are basically wasted. Reps, as noted above, are decreased as weight is increased. For strength/bulk gains, its best to stay at 6 or fewer reps per set.
If you want to feel sore from a work out, try doing some max weight days: a warm up set, then 2-4 sets of 1 rep as you try to lift the maximum weight you can.
Hope this helps.