A love spell is a love spell, it is only your intention that changes whether it is positive (white) or negative (black), in regards to casting a love spell, it is much better to undertake spellwork for yourself.
If you don't know how to yet, then you shouldn't really be thinking about casting one.
I don't know what you mean by black magick. Black magic usually means something negative. Are you trying to steal someone else's lover of something? But negative is really just subjective. If your trying to influence someone to like you please consider how this will effect the person and others. Do you think this will do more harm than good? Are you willing to accept any consequences of your actions? Please run through these questions and take your time.