Contrary to the unfortunate popular belief, honey that crystallizes (gets hard and cloudy) is not bad. This is a good state and will hold its quality for years.
All natural honey crystallizes and becomes hard in its container. There is no way to stop this unless the honey is cooked. Even cooked honey will crystallize with the passing of many months or more.
The best way to liquefy honey is to do as the bees would do. warm it up.
Remember the bees will only bring the temperature in the hive to about 97°F.
Therefore you do not want to take the temperature of the honey much higher. Summer time temperature in the hive might get to 110.
*never hotter than 110°F as the temperature shock could break the glass jar.
Make sure the honey bottle has a clean rim and the top fits tight.
bring a large (2 gallons per pound of honey) pan of water to 110 degrees
place jar of honey under the water. It is OK if only the top of jar is above water as this will ensure no water gets into the honey.
If honey is still crystallized after water has come down to about 90 degrees then repeat until it is liquefied to your preference.
note: sometimes very large crystals of honey will form and be very difficult to re-liquefy. What i would do is when the bottle is empty I will take a cup of warm (>120 degrees F) tea, pour it into the glass honey bottle and swirl it around until all the honey has come loose. pour the tea into a cup and enjoy.