Assassination is a bit brutal, when it comes to PvP.
In an open battle you can sort of "sense" when it's coming. But when you visit a Tavern, start to rest and suddenly a guy pops up from invisibility while you sleep there is just no way to prepare yourself for it, but as was said in the beginning the best way to avoid any and all PvP is to not make enemies with anybody, and if you make enemies make sure it does not reach the point where you want to kill one another.
That said, not everybody will want to outright kill you, and there are ways of running away from PvP situations, such as using Invisibility, knowing the map (to escape somehow) or having enough big friends that your enemies will think a few times before attacking you.
As an example, if you were a Level 3, hunting bandits in the Old Town, and proclaiming every kill you would be quickly targeted by the local gangs and a bounty would be put on your head. If you did not think of signing up with a group, or if you are simply somebody seeking quick fame that would work, but if somebody killed you nobody would seek to avenge your death and you would make a very easy target. In turn, if you signed up as an Agent, built up some relations with the different factions and groups of the city, made your name internally and then proclaimed that you want hunt for bandits you have a substantially larger backing than before, and thus much harder to move/kill.
An example from our server would be Ezekiel. Even if he had a 10,000 gold bounty on his head I doubt there is anybody who would want to touch him because: 1) He is just that high a level not to be messed with, 2) He has friends, or at least people who would prefer to keep him alive, rather than dead, 3) He has made a clear name for himself, over the countless encounters with other PCs and NPCs.
Does that mean you have to be at least Level 6 to start making enemies, or engage in plot that will rub sand in other peoples' eyes? No! You can start doing that from Level 1, but you have to start small and be somewhat smart about it. I mean, V from V for Vendetta did not start his entire operation as soon as he escaped from the facility, he gathered his resources over a very long time. Following a similar example if you had a band of low level Half-Orc bandits you would start by doing some quests, maybe organizing some small events to raid caravans or unimportant settlements, but you would not besiege the city straight away, and you would most certainly not make it a point of honor to make yourself known when you are still too weak to fight off your enemies.
Or my favorite example, if you want to be a Necromancer you will not act like a Full-Fledged Necromancer until you have the power to tell others what you think about local Undead laws. A hidden Necromancer can gather resources through selling wands and potions, he may also quest, by using spells that will not frame him as a Necromancer. Over time he will get the necessary experience, knowledge and items to reveal himself. Doing so early might be fun, but if you wanted your character to survive for an extended amount of time you just have to be careful