I think the biggest mistake most vegetarians make from my observations is trying to dishes where meat is an integral ingredient without meat. Even worse is using meat substitutes. Expand your culinary horizons. There are many many cultures where meat is a special item due to cost and rarity. They have plenty of wonderful dishes which were never designed around meat. Explore mediteranean cooking, Indian cooking, etc. Look for lentil dishes, squash dishes etc.
I am an omnivore, but I can cook dishes which vegetarians love, as I am half Armenian. Vegetarians are easy....weirdo vegans, now those guys are hard to cook for.
Falafel, tabouli, lentil kufteh, borag...etc.
One exception that I do to my own rule is a vegetarian squash lasagna....though sqash lasagna is better with meat...go figure (preferably a nice cute bambi like deer which you ground into sausage).
Take yellow squash, zuccini, or both and slice in slices about 1/4 inch thick. Dip them in beaten eggs then dredge in seasoned bread crumbs with optionally a litte parmesan cheese mixed in. Good seasons itallian dry dressing pack works good for seasoning plain crumbs btw. Fry the squash in olive oil, clarified butter, or grapeseed oil until golden brown and set on a paper towel to drain.
Make your lasagna as normal except use layers of the fried squash instead of noodles. This a a great way to use of extra squash from the garden. And anyone who has grown summer squash knows there is always extra when it comes in.