One thing that I have always been aware of but have noticed much more significantly since I have been personal training, is that people focus a lot on the number they see on the scale. I really like to emphasize with my clients that this is truly just a number and not the be all, end all.
There are much better ways to check progress than the scale. If you are trying to lose a significant amount of weight then the scale can definitely be helpful. The best ways to actually have a comparison is to take measurements and measuring fat percentage. It is possible to measure fat percentage by either calipers or a scale or handheld device that uses an electrical current to detect body fat. I personally prefer the handheld device or scale to calipers because it doesn't feel as invasive. I don't like using calipers on myself, and I have noticed that most other people dislike it as well. However, it is an appropriate way to get fat percentages on the different areas of the body.
Tape measurements are also a great way to tell how much fat you have lost. You may weigh yourself and not have lost much or any weight but you can tell you are smaller, how is that? Well a smaller size of muscle weighs the same as a larger size of fat, so while your fat percentage is going down, your muscle percentage is going up, so the scale may not change much at certain times. However, even though the scale does not change, you can still see a difference and the measurements can change.
On a personal note, I have not changed my size much over the past couple of years, but have toned up. I am stronger and leaner than I have been, but my weight has gone up some. This is because i have strengthened my muscles so much more while still burning fat, so my size is pretty stable, even though my weight may go up a bit when I am focusing more on weight training.
The best thing that I like to tell people is to judge change by how they feel, how they look in the mirror, and how their clothes are fitting. Its possible to tell that you have more muscle on when you feel more solid in different areas of the body rather than a soft or flabby feeling. If clothes are fitting differently then it means your body is changing. These are the important things to pay attention to and the best way to feel the change.
It can be easy to fall into feeling bad when you have been working hard and don't see the scale change. Don't get frustrated so easy and then just give up. Keep working hard, exercise multiple times a week and having a healthy balanced diet and you will see results. Just remember to listen to your body and see how you are feeling. If you go based on that you will be successful.