My tips would be: don't go nuts starting crazy fad diets. Improve step by step - be careful of going hardcore day 1 and then burning out, cheating, or getting "food fatigue" from too-monotonous flavors and quitting.
Advice depends on how healthy current diet is. Relatively painless 1st steps:
Cut out sodas and empty calories completely. Fruit "flavored" drinks suck too - always look at the labels. Even pure fruit juice isn't so great - a LITTLE isn't awful, but better to eat entire fruit so at least you get some fiber. If you're having trouble weaning off sodas, try water with a little lemon, or unsweetened tea.
Move from processed white flour products like white bread/white pasta to whole grain complex carbohydrate foods like brown rice, wheat berries, quinoa. Mix in some lentils or beans for protein.
My go-to meal is lentils or black beans + brown rice/wheat berries/quinoa, cooked in chicken broth in steamer or slow cooker, mix in a cup of fresh or frozen mixed vegetables near the end so they stay crispy. Flavor variations: tomato&garlic for "spaghetti like", kalamata olives + capers + tomato and garlic for "puttanesca" (heh I like tomatos and garlic
), boneless skinless chicken breast under the roiler, hot peppers, salmon under the broiler, tuna&horseradish, really just about anything you can do to rice/pasta/bread. A LITTLE sausage or cheese once in there once in a while won't kill ya, don't chuck in a half pound just add little bits for flavoring - maybe an ounce or 2. I like lentils 'cause they cook in the same time as the rice/wheat and I can dump it all in the cooker at once, with dry beans you have to remember to soak em in advance. Canned beans aren't too awful once in a while, but watch out for the sodium if you're eating a lot of canned stuff.
Baked potato with salsa or herb seasoning once in a while isn't so bad, eat the skin. I even have a little butter or cheese or olive oil, but I'd cut that way down if I was trying hard to lose weight.
Salads are always good, watch out for the dressing. If you're moving from big macs then a LITTLE dressing is a step up. But ideally just use pepper or herb seasoning and other vegetables like tomatoes/onions/garlic/radishes/peppers for flavor. A little olive oil/vinegar isn't too awful either - you do want *some* fat/oil throughout the day but use your head about the quantities.
Breakfast - oatmeal maybe with a little honey and/or nuts or fruit. Grapefruit is nice. Eggs aren't too bad a couple times a week, obviously don't fry em - poach or scramble. I usually scramble 'em in the microwave with some onions and maybe a little parmesan cheese, or green peppers, or salsa. I like muesli once in a while, mixed with milk or yogurt.
I moved to "smaller meals more frequently" - the theory being that big meals stretch out the stomach more so that you get in the habit of NEEDING big meals to feel full. Instead I snack on nuts&raisins, or greek yogurt+fruit, or celery or salads. Brown rice cakes or (unbuttered)popcorn. Special mention for blueberries, man I love blueberries.
Eat slow, chew a lot (I chew a LOT), drink lots of water. Take a break after a plateful and see if you feel full - you'll get a feel for the right portion size.
Obviously figure out if you're allergic to wheat or dairy or something, if so DUH avoid it.
Stay completely away from the processed food aisles in the grocery stores, you should be buying only raw fruits and vegetables, bags of grains and beans, small quantities of raw meat & fish. Don't even keep bad stuff in the house - if the only snack is celery you're likelier to eat it than when it's a choice between celery and ice cream...
To keep your energy steady, keep yourself topped up with the right mix of foods. Fruit will give you a quick sugar boost, protein and complex carbohydrates will give you energy over a longer period, a LITTLE fat like from nuts, oily fish like salmon/tuna, small amount of olive oil on salads is vital, and helps you feel fuller longer. Even a couple squares of dark chocolate isn't too horrible once in a while - obviously don't gobble down a half pound at a time.
My opinions, read up and test out what works for you. Good luck.