Among all the restaurants in London's 'Little Arabia,' you'll notice a chain of about six Maroush restaurants. (From what I've learned, Maroush is about the English equivalent to Smith or Jones). Skip these places in favor of the inexpensive, independently-run Meshwar. You won't like the decor at Meshwar--unless you're a fan of 1970s posters featuring Middle Eastern rock formations, that is--but the food at this delicious Middle Eastern spot (in the guise of a hole-in-the-wall) is the best in London.
Located next to the bustling Coffee Republic, Meshwar serves mostly locals, and its fresh falafel and complimentary starter veggies keep it afloat but never crowded. Don't be alarmed when you see brains and other frightening options on the menu; the staff here is super-friendly and more than willing to explain what's in any certain dish.
Just plan to stay a while, and be sure to finish off your meal with some mint tea and nomoura (wheaty Middle Eastern pastries softened by honey and rosewater).
If it's fast food or a sandwich instead of a sit-down meal you're after, look for the neon lights of Ranoush Juice (also on Edgeware Road, about two blocks north of Marble Arch tube station). Perfect for a picnic in Hyde Park, its chicken or lamb sharwarma sandwich, complete with pickles, tomatoes, and delicious garlic sauce, represents the closest thing to a Middle Eastern cheesesteak. The Arabic music is always blaring at Ranoush, and the juice shakes are first-rate. Order/pay first, then give your ticket to the guy behind the counter.