I usually don't use one for the first playthrough and just see where I happen to end up, if I liked the choice process of the game I may even go for a few more times while savescumming, in predictable moeges I try getting the (expected) worst girl first, then my completionist OCD kicks in, I look up a walkthrough and play all good/neutral/bad endings, get every CG and often I even read the sequels/extras/spin-offs to the VNs I didn't even particularly like, repeating the process... Don't be me.