So it's been a while since I weight trained and I'm not to up on how many reps and sets are effective these days. I do upper and lower body 2xs (Tues, Fri). I do 3 sets in reps or 8, 10, 12. I then do some varing abs work on Mon/Wed. Also how much weight should I be lifting for maximum effectiveness? My goal is to be lean, not to muscular and I'm looking to lose inches/weight and fat. I heard that I'll know I'm lifting enough weight when it is very difficult to life that last rep. Is this a good gauge?

Yep - that's the best gauge...8-12 reps of a weight that makes it very difficult to get out your last 1-2 reps in a set. You should have to *really* work for the last few.

The amount of weight is very individual so no one can tell you the right amount of weight for you. There are also different methods of lifting weights which include anywhere from 2 to 5 sets. I like increasing the weight with each set and possibly lowering the reps if need be.

Lifting to 'failure' is a good gauge. Which means you really have no more reps in you, I would expect your last set to reach failure/near failure if not your last 2 sets. Of course remember form is important.

Also, are you doing free weights or machines? If you are doing machines, I would urge you to work your way into free weights. If you are already doing free weights then excellent!

Also, how long are you spending on Monday/Wednesday? I really wouldn't dedicate entire workouts to just abs. It might be better to split your workout up a bit such as an upper/lower body split adding some abs into part of one or the other.

Good for a beginner. As the weights get heavier, it is a good idea to stop a rep or two short of failure to keep from overtraining. I didn't used to think you could get stronger without training to failure, but I understand now how quickly failure leads to overtraining. Now I generally increase the weights when I can easily complete all my reps and sets, with a rep or two in reserve.

Once you get past the initial gains "body building" is really hard and takes tremendous attention to diet and training volume, so I wouldn't worry about getting "too muscular".

I run Mon/Wed and only spend about 15 mins on my abs. I also run Sundays and Hike Thursdays, but no muscle work on those days, there is no time. So Tues/Fris are really the only time I have availble to hit the weights and since they are 3 days apart I figured do upper/lower the same day would be ok and better than only getting one day per section.

Ok that makes sense. And yeah full body workout is probably better if you can only do twice per week.