Weigh yourself often
Weighing yourself at the end of each week works for some people, but not me. I find that weighing myself often is one of the best ways to keep myself motivated. I get to see my progress every day, not just after one week.
If you don't have one already, get some digital scales. Find ones that will let you see the difference to 0.2 of a kg (or lbs). When you see yourself lose just that tiny bit, you will feel very good about yourself and be motivated to keep on going. If you gain 0.2 or 0.4, it is a lot less disheartening than seeing yourself gain 2kg's at the end of the week! It will make you try harder the very next day and you won't feel like giving up altogether because it is only a small amount you have gained.
I find hopping on to the scales just before bed works the best. This will be after you have had all your exercise, all your food, finished for the day. This will give you the most accurate reading of your performance.
Remember, motivation is the number one, absolutely most positively important thing you need if you want to lose weight! Putting this suggestion into practice will give you lots of motivation!