Depending on when your last physical was, I would start with that. An annual physical will include blood work to show if there are any specific things you need to alter in your diet (i.e., reduce carbs if you are pre-diabetic, watch sodium if you are hypertensive, limit saturated fats if you have high cholesterol). Your physician can make suggestions about what kind of diet will be best for you in terms of weight loss and overall health. If you have insurance, call the number on the back of your ID card - they can help you find a primary care provider who can give you a physical. In terms of general guidelines to get started, try to get 30 minutes of physical activity each day. Walking is easy on the joints and all you need is a pair of sneakers. Even if it means walking 10 minutes before work, 10 minutes at lunch and 10 after dinner, it still counts. Personally, I spend too much time at my desk, so I just zip around the block a few times a day. For diet, I use My Fitness Pal to track what I eat, my activity each day, and my weight. It keeps me honest - if it goes in my mouth, it goes in the app. It helps me track my calorie intake and nutrients since I am trying to lose weight and lower my carb intake. Good luck.
You may want to look into scheduling a bodpod session. You should be able to google which location near you provides that service. They typically have nutritionist available to assist also once they get your stats from that session. You can more effectively lose weight if you know what is required for your body's caloric intake from a bodpod and able to factor calories burned from any physical activity you add. Just keep in mind that healthy weight loss is 1-2 pounds per week if you are wanting to avoid excess skin, possible bowl issues, and stress on the heart from losing weight too fast.