1.Dont fall for low introductory rates. These can increase dramatically
2. Find out what others are paying and ask for the same rate.
3. Ask for free training sessions as a condition you will join
4. Find out if there is a membership limit. If not the gym could be very overcrowded at peak times.
5. Wait until march. The initial rush of New Year’ resolution joiners will be over and the gym may be more willing to negotiate.
For more info read this excellent article from marketwatch.com