Depending on what is the function of the pin and how it affects the overall function of the chip you can tie it to ground or Vcc via a resistor.
It is not good to leave floating inputs because they acts like small antennas and they pick up noise.
There should be some. Learn to use google, type the correct words and make the search. You will find many. For example, try to search for "floating digital inputs".
There are a couple of exceptions to mik3's advice. Standard TTL and any of the older TTL families (74Fxx, 74Sxx, 74LSxx) all need pullup resistors to safely tie to Vcc. If the input shorts, the conduction with a direct tie may be haevy enough to destroy the power supply.
Each and every unsed input must be connected so as to be in a known state. If not, the input floats up to the activation level and will cause an oscillation that can destroy the IC, or place so much garbage on the power bus that the entire circuit becomes unstable.