Tel Aviv is a walking city. The original 1909 grid runs north from Jaffa to the Yarkon River, and most of what is worth seeing sits within that strip. The four anchors of any visit are old Jaffa at the southern end, the Bauhaus White City around Rothschild Boulevard, the Carmel Market on the southern edge, and the beach running along the entire western side.
Beyond those, the city has good art (the Tel Aviv Museum of Art is the standout), strong contemporary architecture (Sarona, the new museum extensions, the towers along Rothschild), serious nightlife around Lilienblum and Allenby, and the Mediterranean ambient that makes the whole thing easier than its political setting suggests. Pace yourself: it is hot from May to October.