Burn your soy candle until it is melted completely across the top. This will help prevent your soy candle from tunneling (burning down in the center). 

You should burn your candle 1 hour for each inch of its diameter, until you receive a full melt pool (soy wax is melted across the entire top). A candle 3" in diameter should be burned for three hours to establish it's memory. This allows your candle to get its full melt pool which will increase the scent throw of the candle. If a soy candle isn't given a proper memory burn, especially on the first burn, it can cause your candle to not provide a good scent throw.