So you're playing a Necromancer. You are a "Bad Guy", or at least generally seen that way by the rest of the population. As the only class where PVP is functionally mandated and to be expected, it will probably prove beneficial to you to understand how best to fight against other players.
In following posts I will address: Training, Spells Usage, Zombies and Constructs, General PVP and Various Scenarios to combat specific classes and spells you might run across.
The basic principle is this though: While Necromancers lack in the pure firepower of the Barbarians, Thieves, Rangers and WMs, and while they don’t possess the broad array of debuffs and disablers that MMs and Clerics have, they make up for those wants with stealth and surprise. They sneak in when they aren’t expected, slice and dice their opponents up, and sneak out. The other classes call them abominations and monsters, so you might as well act like it lest they be disappointed. At the risk of sounding dramatic, Necromancers are what goes bump in the night.