Split your goal of losing 30 pounds into smaller, more manageable goals. If you have three months, that means you only need to lose 10 pounds a month to meet your final goal.
Take a hard look at your current diet. Temporarily changing small parts of your diet will not result in meaningful and sustainable weight loss. Cut out as many extra sugars and calories as possible. For instance, the "American Journal of Clinical Nutrition" estimates that women can gain an extra 15 pounds in a year by drinking 12 ounces of soda a day.
Consume fewer calories than you burn. Every food item you eat carries a certain number of calories. Calories are burned like fuel to power your body through the day. Any calories you do not use will become fat. The only way to lose weight is to burn more calories than you intake.
Exercise at least three times a week, and be active on the days that you do not. No diet is going to burn extra weight for you, so get ready to hit the gym. If you do not have a gym membership or are very out of shape, simply walking around the block a few times is a step in the right direction.
Make healthy eating and exercise a part of your life instead of an inconvenience or quick fix. A healthy lifestyle will help you keep weight off, and you will feel better and have fewer health risks in the process.