If you want to avoid soot of your candle, use a match to briefly dip the wick into the liquid wax. Also be aware that paraffin wax candles burn very quickly and produce a lot of soot. A good alternative to this is, for example, rapeseed wax or soy wax, as both burn for a very long time and are soot-free. 

What you can also do is, to trim the wick or the "crown" of the wick to avoid burning for too long. As long as the duration of the soot does not exceed 30 seconds, the soot duration is within a normal range.