The sabotage quests run in series, the first ten (speaking from Qeynos point of view, but I don't think it differs much with Freeport point of view, just change the name of the zones) you have to do 'things' in Commonlands.
These are extremely easy if you are a level that the mobs in Commonlands are grey to you, and involve nothing much more than just finding an object and rightclick it. About 2/3rd of 1% xp at lvl 26, lol, which is actually a lot for doing nothing more than running. Some of the quests take some time, either I looked at the wrong place or you do have to wait for spawns of the item you need. (5 items needed, always)
The next tier of quests involve going into the suburbs and destroy items there, and that's where the fun starts lol.
I haven't been able to finish a quest involving the suburbs, as yet, but a fellow guildmember did several already. The trick is getting to know the route of the guards, they will kick you out instantly if they find you (a pity, I'ld love to be able to fight them, fighting Freeport militia would bring back memories, lol). Another necessity is remembering where the object is that you are looking for, not always easy as apparently the objects have more than one spawn point.
hint for these is never to accept the mission before you reach the marine bell, that should save a minute or two.
I wonder what happens when you have done the ten quests in the suburbs, might be another set in the city itself and then perhaps the citadel?
Getting to the Commonlands isn't exactly my idea of fun though, it involves running, almost inevitable that you get a tag running through Nektulos. Only died once so far though.