Okay so I have been exercising for quite sometime now and have tried different things, at one point I was working out three times a week doing at least one exercise per muscle.

Then I was doing two exercises per muscle and started doing protein shakes and bars and all the other stuff.

Finally a got to a point where I was doing one muscle group a day with several exercises i.e. I would do like five exercises for my chest on a Thursday.

My question is what is the best way to go about doing an exercise regiment that will not only work but allow me to get bigger and more defined.

There have been slight changes over the last four months but very little to say the least so any adivce would be appreciated.

To build muscle mass you need a good natural diet and a great overall workout program, Not just one area, work/train the entire body! The workout is making your body build muscle tissue. You need stores of protein to make this possible. So your diet is # 1 to check out;
Eat lean meat--Rich in protein, meat like chicken, turkey, steak, fish, but avoid fatty cuts, and skins. Eat at least 1 gram of protein for each pound of bodyweight, when you sart to get serious and have a reall exercise program.
Fiber rich foods, wheat, veggies, fruits, oatmeal
Soy bean, great source of protein, and no cholestrol, 1.e. tofu, bean curd are some versions)-
Water, drink a lot workouts dehydrate you
Whey protein- taken as a supplements, mixed with drinks, shakes, veggies, soups, its one of the best proteins and easy to digest
Egg whites- Protein is in the whites not the yolks
"Quality Sleep" very important, weather it be 6 hrs or 8 hrs.
You need to train the "whole" body not just one area, weights will increase your lean body mass-squats, bench presses, deadlifts, shoulder presses, (compound free-weight exercises) barbell rows, this is what you need to do to get more mass, walking or jogging also. Get with a gym or ymca and see what progams you can get into. 4-5 times a week 30-60 minute sessions for the whole body.

As mentioned, for mass you really need to challenge your body. It is actually not natural for your body to "want" to put on extra muscle mass. You have to stress it into doing this, safely of course. And maybe your routine has become too "routine" and your body isn't responding.

And then there's genetics. You might find it harder to put on more muscle mass than others. Genetically, I have always has an easy time building mass in my arms and chest. Guys in college would get pi$$ed cause id look better then they did working out a fraction of the time.

Conversely, I've always had to work like hell to keep my waist and legs thinner and more defined. I just naturally carry weight there faster, and it's a pain in the arse. If I didn't have the bigger upper torso to balance out the bottom, id have some problems. Just genes.

So, get a good weight training program going. This means changing things up also. If you are doing the same routines, even with heavier weights, your body might get "used" to it. Cross training or doing different work can help keep your body "guessing".

If you struggle too much with gaining mass don't go nuts. A guys with less mass but who is cut well can look every bit as good. I have a friend who does landscape work. He doesn't appear to be especially muscled when you see him... maybe even on the skinny side. But when he takes his shirt of to work you know damn well this guy is fit.

So focus on health first. And the point about rest and recovery time is critical.

I agree with what was said about the Y or a gym. Fees can be cheap (the Y is absolutely affordable to anyone) and you can get help designing workout plans. Someone else working with you can mix things up and give you fresh angles to try.

I've got a good starter mass weight training program around here somewhere ill try to find.

more random thoughts...

muscle mass has nothing to do with minutes in the gym. It has to do with stress and hard reps.

your body won't build bigger mass unless you are increasing your weights over time. If you are still working with the same or nearly the same weights as you were before, why should your body make bigger muscles? It costs energy. It takes maintenance. You are trying to force your body to go against itself. This means really stressing the muscles. 8-12 reps, hard work. Don't be doing the same weights a month or two later. You need to stack more on. If you've been working out your body should be broken in enough to be upping the weight and increasing the resistance.

its fine that you work your whole body, especially as a beginner. When I was established into a hard routine I split my workout into diff parts.. one day legs, abs, chest, triceps... another day back, shoulders, abs, biceps. Alternated every other or third day... so one day workout one, one or two days off, next day workout two, one or two days off. Cardio here and there.

its fine to do 4x a week but if you are really looking for muscle mass, you might want to cut back to 3x, make sure you are really working hard (but w good form and safety), and give your body a day in between to recover.

if you want arm mass don't neglect the triceps. Everybody works the biceps w curls, but you can really get some good mass w tricep work.

doing chest work at diff angles and a mix of presses and flys is needed.

when doing abs you need to really squeeze the muscle... not just raise your torso. And a mix of crunches, side bends and tilts will help hit all the angles.

flab or fat isn't going away by weights. It takes an overall reduction of fat, which means proper diet and cardio.

one of the best things I did when I was a teen was I bought a body building book. I didn't want to be that bulked, but it was really good about explaining proper form and how you could vary different exercises to hit different angles and muscle groups. If you don't have access to a trainer at a gym (if there is a ymca nearby you can get a membership easily) you might want to do a little reading.

so you need to really push your body, using good form, being safe. If you are doing the same old routine and not getting results, then you need to amp up your routine

Just a quick follow-up question is it best to do one exercise per muscle or to do maybe two or three per workout for each muscle?

If you're looking primarily to build muscle, you should do multiple exercises per muscle group.

When I'm doing a building cycle, I go to four workouts a week, one day each for the following focus areas:

Day 1: Knee-dominant lifts (lower body)
Day 2: Horizontal push/pull (upper body)
Day 4: Hip-dominant lifts (lower body)
Day 5: Vertical push/pull (upper body)

Each workout should start with a solid stretching routine and two or three light exercises for the target muscles (using low weight, just to get them moving), four exercises with full weight, and two or three light exercises again to cool down and stretch afterwards.

For the sets, reps, and weights, use the following rule of thumb:

Warm-ups and cool-downs, one set, fifteen reps, and extremely light weights... if you don't feel silly for the weights being so small, you're using too much.
Main exercises, five sets, four to six reps each (start low and build up to six reps, up the weight a step, and go back to four reps). You should start with the weight about 10% above what you're lifting for 10 reps, and build from there.

Remember, you can SERIOUSLY hurt yourself doing this type of routine if you don't take your warm-ups, cool-downs, and weight/rep combinations seriously. Don't get aggressive on the weight increases, and don't skimp on the light stuff. You should also avoid doing these heavy routines for more than eight weeks or so before switching back to a more balanced routine... your joints need that time to rest up or you will injure them or the connective tissues. I'll usually do a heavy routine like this for eight weeks, take a week off, then to four to six weeks on a circuit before going back to the building cycle.

I'll pull up one of my old routines when I get home from work to give you an idea of what to start with. When putting together any routine, remember that if you're focusing on one muscle, you're not lifting responsibly.

Here we go... my last 'build' cycle: Six exercises done in supersets per day... four for the primary motion groups and two for supporting muscles. This is an ultra-aggressive plan, and I was doing three sets in a pyramid.

Day 1: Knee-dominant
Front Squat/Lunge
Hack Squat/Seated Calf Raise
Cable Crunch/Reverse Crunch

Day 2: Horizontal push/pull
Bench press/Bent row
Inclined fly/Rear lateral raise
Bench preacher curl/triceps extension

Day 4: Hip dominant
Deadlift/Lying leg curl
Step-up/Calf raise
Hanging leg raise/weighted crunch

Day 5: Vertical
Pullup/Military press
Upright row/dip
Hammer curl/tricep extension.

Each day I would start with very thorough stretching and 10 minutes on the treadmill at a light jog, then do a set of each of the first superset with almost no weight (20% of working weight) for 20 reps, and then a second set of those with medium weight (40% of working weight) for 10 reps. For cooldown, I'd do the second superset with light weight (25%) for 10-15 reps (excepting the purely body-weight exercises like pullups... for those, I used the resistance exercise from the other superset)