One of the most common reasons people don't get results is they go to the gym and just do STUFF. No plan, no rhyme or reason, they will just go workout.
Don't get me wrong this is MUCH better than doing nothing at all. The problem here is that begin to think that exercise does not work. "I worked out every day for a month and got nothing to show for it!"
My tip for you is to always have a plan before you start your workout. There are so many things to take into account that it gets pretty complicated and you can get overwhelmed. When I design workouts for my boot camp or myon-line personal training business I have 7 things in mind.
1.Which exercises I want to use
2. What the goal of the workout is
3. How to make each exercise harder/how to make it easier
4. What order the exercises will be performed in
5. What speed the reps will be performed at
6. How much of the exercise will be done (sets, reps, time, etc..)
7. How long the rest breaks will be
These are the types of things you should have in mind to make your workouts more efficient and effective. It is a lot of work to put in, but the results are worth it. Or if you have a current plan and you are looking to change things up, think about some of the options above. It is amazing the difference just slowing down your repetitions or decreasing your rest breaks can make.
If you need more help or clarification on this please let me know and I will be glad to help.