If you like eating meat, I see no reason to go fully vegetarian. Meat is good protein. Vegetables to the exclusion of meat is not necessarily healthier. It's more a matter of balancing the protein, carb and vegetable, along with a little of a good fat. (Yes, the right fat is good for you!)
1. Start with 4 oz of protein.
2. There are lots of veggies that you can eat in "unlimited" amounts: Broccoli, asparagus, kale, spinach, romaine, celery among them.
3. Toss in some good fat: almonds, 1/4 cup cottage cheese, a bit of butter to sauté the veggies in, olive oil, peanut butter, 2T cream cheese
Eat 3 balanced meals a day, and 2 snacks (same proportions as meals but half-size). A small snack before bed may help as well.
Also, be sure to drink lots of good ol' H2O .. 64 oz of water a day is recommended. (And do-able, though you may have to work up to it if it's not already a habit.)
I started eating like this and I couldn't believe how much food I was supposed to eat (and to lose weight, even!) I like meat so it's what I eat. If you wish to go without, replace the meat with equivalent non-meat protein. (Vegetarians would be more helpful with suggestions there) Protein is the key to feeling satisfied till the next meal.
Meal 1: 2 Eggs, 12 spears asparagus, 2Tbsp butter to sauté it all in
Snack 1: Small protein shake (1/4C plain full-fat yogurt, 1/2C frozen fruit, 1T coconut milk, whey protein powder)
Meal 2: 4oz turkey, 2C Kale or Romaine, 1/4 c onion, 2Tbsp dressing (vinegar/oil is yum!)
Snack 2: 2 oz beef jerky (look for the good stuff, no nitrates/nitrites), 1/2 apple with 1Tbsp peanut butter
Meal 3: 4oz Chicken breast, 2C broccoli, sautéd in a bit of butter, with seasonings of your choice
Snack 3: 1/2 c Raspberries with 2Tbsp whipped cream (whip your own if you can, then you're in control of how sweet you make it. I like to add cinnamon to mine!)
While I was writing this, WillyNilly made some excellent suggestions. I love her dessert option!
Beware of "low-fat" and "diet" versions of anything. Often things are added to create the flavor removed with the fat/sugar, and the replacements are worse than what was removed.
Quinoa is excellent. You can buy it on its own ready-to-cook, or, Trader Joe's has a frozen quinoa with some veggies mixed in. A quick heat-up in the microwave and you've got half your meal! TJ's also has excellent jerky, and a whole aisle of various nuts.