A dripping candle can have a number of causes. Fortunately, if you're burning a well-made, good quality candle then all these issues can be easily remedied; it's just a matter of determining the cause and knowing the solution. So let's get started.
A strong draught can cause molten wax from the wax pool to get blown over the sides of the candle. Eliminate the source of the draught, move the candle out of the draught or shield the candle from the draught.
If the candle is too close to other candles, this can cause irregular melting and warping. Place lit candles at least 10cm (3 inches) apart to avoid melting and warping due to heat from neighbouring candles.
It could be that your candle has been placed at an angle - make sure the candle is standing up straight.
4. Burn time
When you first light your candle, burn your candle for around 3-4 hours; you want to get close to the mantle to avoid tunnelling, but you don't want to melt through the mantle. As a rule of thumb, burn your candle for 1 hour per 2.5cm (1 inch) in diameter the first time you light it.
After the first burn, avoid burning your candle for longer than 4 hours; extinguish, let the candle cool down, trim the wick, and relight.
If you notice your candle (might start) dripping, check the wick; it could be that the wick is too long, causing a large, flickering and unstable flame. Extinguish the flame, let the candle cool, trim the wick down to 6mm (¼ inch) and relight.
Hopefully this helps you prevent your candle from dripping. As you see, most of the causes can be easily fixed and avoided, and if they cannot then it's more likely a symptom of a poor quality candle (low quality wax, incorrect wick size or positioning, poor make quality) rather than incorrect use of the candle.
For more tips & tricks on how to burn candles, please read here.