Or any tips would be appreciated. I haven't experimented much with it but I wondered if there were any tricks to doing it effectively.
If you're out of target-lock range (and in long range), you can use a shortbow (lowest min stats) to target with crosshairs and switch to catalyst and cast spell. The spell will go to exactly where you aimed with the bow. Takes some practice to quickly target and cast but gets easier. If you're griefing on the Anor Londo rafters or sniping bridges, you can just target where they have to move across and switch to catalyst and just lie in wait without moving. When you cast you're still good on the aiming if you haven't moved.
EX: targets with bow and then casts spell (one-shots Ingward): http://www.youtube.com/watch?v=-VbllEm9ozw#t=63m25s
If you're talking about closer range, you can click target-lock quickly on/off if you don't like target-locking or just dial-sweep if you never target-lock but that takes lots of practice to aim consistently imo.