1) the way I undrestand it, there is a timer on certain quests and npc's so that the same npc isn't giving out the same quest every 5 seconds. but his I have only seen with more of the harder ones, that give better rewards and such.
2) normally, "do you need something", a variation of that, "give me a quest", stuff like that works well. There are some quests that will require the npc to get to like you ( as in, you have to ask how they are doing, then ask about things it says in its response, etc. You know, hold a conversation with it.) after all, when the npc system is completed, it should be no different than holding a nice conversation with one of theem IM bots. and those can be quite fun sometimes.
Unfortunately, it sounds like you may not be wanting to stick around that long, as it will take time, just as everything else does around here. I welcome you to stay and participate in testing things, making friends, engaging in the RP, but you must remember that you are a tester first and playe second, and that this game is still in early developement. Hope this helps.