Since the basic idea of a competitive MMO is to stop all others from getting somewhere so you are the only one to have fun, here some basic guidelines
General rules of behaviour
Quell potential rivals as soon as possible (eg. by simply destroying all their stuff, optimum is to do it before they manage to claim it) before they become a threat.
Limit opponents movement by steal or destroying any boats you can find (preferably while the owner just stepped out of it)
Denying others access to resources (quality nodes, caves) through claim alts (creating one is possible for <5 minutes of actual work, just spawn one and feed some leftover curiosities) is a must.
Don't forget to spoil everything you are not interested in using so others can't benefit from it.
Howto: 5 steps to Steal and Murder without leaving scents
3 people in boats vs. 1 unsuspecting victim
1) position around the victim so he can't move anymore
2) destroy victims boat
3) watch him drown
4) laugh your ass off
5) pickup the containers that were inside the boat
This is also fun on people who are afk fishing and can be done solo in this case.