Unlike other cities in the western world, in Tel Aviv, Taxi transportation is relatively inexpensive. There are lots of Taxis around, and they are required by law to use a meter ("Moneh").
The cost of a taxi drive from one end of the city to another shouldn't be more then 30-40 NIS (Shekels) or $7-9. A taxi from the hotel area near the beach, to most central places, usually costs 15-25 NIS, depending on the hour and traffic.
ALWAYS ask the taxi driver to use the meter (say "Tafiil Moneh"), even if he suggests otherwise.
One easy and cheap way to travel around is by the Sherut Taxi's. they can take up to 9 or 11 people (depends on which kind of Car they use) and its much more comfortable then using a buss.
The prices are normally cheapr then buss.