How does necro aggro work?

[luckynclover]

Trying to figure out how aggro works with necros in relation to when i cast spells and aggro from my pet? So say i attack a yellow con mob ill send in my pet. About when can i actually start applying my dots to said mob without ripping aggro from my skelli? Seems like anytime i cast a spell before 75% i get instant rippage?

Can someone give me a quick how to of when to apply spells so that i dont rip aggro from my pet? thank you!