Here's a good one:
Eat only when you're hungry until you're full, no more, no less.
Also remember to eat breakfast every day because if you don't, studies show that later in the day you are more likely to eat lots of unhealthy foods to fill yourself since you didn't eat breakfast.
Only consider losing weight if you're overFAT, not just a large number on the scale. There are TONS of variables that affect weight, which is why there is no real average weight for anyone. Height, bone mass, bone density, and muscle all affect weight. There are lots of tall people are skinny that weigh more only because they are tall and lots of strong skinny people that weigh more only because they are strong and muscle takes up a lot of weight.