To enter PVP a player just needs to enter a PVP area, marked by a red glowing border, either in the Ice Wind Pass or Dwarven Valley.
Once they enter they are then flagged for PVP. This means that that can fight anyone of the opposing faction that is also flagged for PVP anywhere in the zone, not just the designated PVP areas. Till you leave the area or find yourself at a fireplace.
PvP BID event
Once every while the BID event comes up. See here for instructions on how to win.
You can also do PVP in a party and so engaging other parties. But the fight are always calculated by the player. So you might die, but you're party member will continue.
This flag is removed when you die or when you approach the zone exits, campfires, or relog. So it is easy to remove if you want to get out of PVP. It’s easy to recognize someone that is flagged for PVP because their contract symbol over their character will be brightly colored instead of gray.
In the PVP areas of Curse of Icewind Dale players will find the PVP specific quest objectives. These quests can help the player earn a little more XP and coin. There are NPCs and other items in these areas so players can complete quests. Players just need to keep an eye out as other PVP players can attack while you are doing these other quests.
Players who mine Black Ice in the PVP area will earn more than the safer areas outside of PVP. The base for each time a player mines is 60 in a PVP area as opposed to 50 outside of a PVP area. If nothing else, it’s worth stocking up on raw black ice in the PVP areas.
There are a few things that all players will likely want to earn whether or not they really enjoy PVP:
If players wish to participate in the PVP pieces of the daily grind they should either do them first or last. It is not a good idea to bounce in and out of PVP unless you do not mind dying and frequently or unexpectedly, loosing whatever buffs and potions you have used.