The key is to not do the same thing every time. Do some excersizes and then change your routine and trrck you body into doing something else. I usually alternate between upper and lower bosy throughout the week, but even on upper bosy days, I'll work triceps one time, then chest and biceps another. It's good to be at a gym where you had plenty of options.
I've finally joined one and have noticed results faster than anything else I've tried before. I've been to the gym half-heartedly before, I've had weights in my house, and I've tried the pure cardio route (cause it's better than nothing). I usually do 15 minutes of cardio, 20 of weights however that may be, 15 minute cool down walk, and then 10 of core strengthening. Which I may add is very important, since all your other strength stems from that. It's amazing how much your shoulders and abs play in the rest of your strength.
Technique and routine aside, Nik hit it on the head. Low weight/high reps will tone you, high weight/low reps will build muscle. Which is why I try to avoid jogging. You build fast twitch muscles, whereas I do barbell squatting with heavy weight. You won't be a marathon runner, but you can sure squash the heck out of fauxkley's after punching them off someone's face. I'd recommend no more than 15 reps on any given weight practice. Abs you can go higher, since you're not using as much weight. You're own body weight is plenty enough for any core fitness.
For upper body, benchpressing is good for chest muscles. Alternate between lying flat, decline, incline, and sitting presses. Dumbells or anything you lift behind your head are good for triceps. Curls, are good for biceps, but don't limit yourself to those actions. Try new things, and lift weights in ways you haven't before. Also the more you lift weights away from your center of balance, you get the added bonus of core stabilization which will work out even more muscles.
For lower body I'm always doing barbell squats. You get the barbell on your back (hopefully you can find a rack to have it propped on), then lift off and dip until your upper leg is parallel, then back up. Leg curls and all that is good too and should be worked in, but squatting really targets most of your lifting muscles.
In addition to reps, every once in a while try testing your max. This is a good way to see your progress. If you need to guesstimate, you can find out using this form I wrote based on your reps and weight.
http://dcj.amaltd.com/DCJ/Weight/VMaxCalc.asp
For example, I can squat 225 lbs (102k) 15 times, so my estimated max is 331 lbs (150k). Right now, I'm at a 315lbs max, but I know I can do more. I've been up to 345lbs, but I've been off my game for a while.