How to reproduce meat flavor
I am definitely not a vegetarian, but I do love vegetables. The flavor of meat cannot be reduplicated by vegetables, but there are definitely certain things you can do to help.

Smoke Seasoning
Two common varieties are liquid and powdered. Usually, when I think hamburger, I think char-grilled. Liquid smoke can be incorporated with certain things to enhance the flavor. I suggest to use liquid smoke sparingly as it is quite concentrated. Also, grill seasonings often contain smokey elements of flavor.. for example, mesquite seasoning and a plethora of other of other grill like seasonings are very common in your traditional American grocery store spice aisles (including liquid smoke). Alternatively, grilling your veggies and using good wood (mesquite, hickory, etc.) will impart a nice flavor.

Veggies and vegetable products
Of course, with any non-meat entree choices, it may be hard to feel 'full' after eating a meal. I'd recommend vegetables with a relatively high protein content to offset this. Garbanzo Beans (chick peas), and really any derivative of a bean are good choices. If you can acquire a taste for tofu, it is an excellent medium of absorbing flavors. Zucchini, asparagus, string beans are also great additions to any vegetarian meal.

Texture
When I think of something meaty without the meat, go with fungus! Mushrooms are excellent options, provided you have a taste for them. I sometimes make sandwiches with thick cut slices of portabello mushrooms that are stir fried with a savory sauce. Mushrooms provide a meaty/chewy consistency and are also great conduits of absorbing flavors. There's always much room for mushroom in my cooking repotoire!

Dairy
Provided you are not going "vegan", using cheese as you would with meat is excellent in providing that extra "oomph", especially in sandwiches. I do not know many people who dislike a grilled cheese with tomato soup. Mozarella paired with basil, tomato, and other herbs is also great on sandwiches. Also, think of mac &amp; cheese and alfredo sauces for pastas. Throw in some versatile veggies you like and you have a full meal right there.

I'm not opposed to vegetarians, but I do feel that meat has played a huge part in the evolution of the human species. I believe it is your freedom to choose whatever you want to eat. In the end, my advice is to really expand your horizons for flavor and adapt to all the wonderful veggies this world has to offer. Indian, Middle Eastern, and Asian cuisines usually have great choices for vegetarian options. Also, if you are philosophically okay with being a pescatarian, seafood options are plentiful.