Bluelady, like any tools of divination you do have to be careful. Especially with quartz because of it being an amplifier crystal. This advice works for any and all crystals you get. However certain ones can not be put under water so investigate or ask the shop you buy from about cleansing it.
So first steps first, before you use your pendulum or crystal, wash it under warm water while saying "all negativity on you is now being cleansed and washed down this drain."
Step two, imprint right away on the crystal what you want it to do. They are programmable. :) And always end your imprint with "for the highest and best good of all"
Step three make sure you do some kind of ritual of protection on yourself before doing any kind of divination. If you need to learn this, check out the forum. If you can't find anything then just p.m. me and I will be happy to tell you the one I use.
Step four make sure you close all openings you have opened in search of the information. If you don't, you leave a wide open door for things to come through. This is something I wished someone had told me when I first started working with my pendulum. I like to say "I now close all open windows, doors, vortex's or any other kind of gateway I have opened as this session is not closed." Now being the rather safe than sorry person I am, I like to add "To all dimensions, all realities, all realms in all universes and time frames." in my closing ritual. Makes it a bit long winded, so it's up to you which one you chose to use.
The reason for cleansing is that you don't know who came into contact with that crystal by touching it. Therefore their energy will be on the crystal. So if they are having a bad day, that kind of energy will be on the crystal. Which you don't want. You want your energy imprinted upon it. This is why you will often see "never approach any divination if you are angry" For one, you have now imprinted the wrong kind of energy onto your tool/tools.
Here is another good practice to get into. Never ask questions concerning another without their express permission to do so. It's a psychic form of invasion of privacy. You wouldn't want someone nosing around in your privacy, so be respectful and do the same. Also, you may get the wrong answer completely by not asking the question the right way. It is very important to know how to ask questions with these kinds of tools.
There are good trustworthy boards out there on pendulums and dowsing. You don't have to be a member to use them either so only pay the fee if you can actually go to the things they offer. I use a lot of boards, all over the world. The American Society of Dowsers, The British Society of Dowsers, The Canadian Society of Dowsers, The Australian Society of Dowsers, just to name a few.
A good site to go to for information on crystals and what their properties are is the crystalvaults.com Free Guides & Resources you don't have to buy from that company, just go there to learn about crystals.
You asked about how to get an accurate answer. Because of the multidimensional theory I like to say "In this reality, in this time frame, in this universe is where I want this information to come from." It makes sense if you think about it because unless you tell your tool where to look, it could be out there reading from another time, space, reality and universe.
I hope this helps to get you started better, if you need me, be happy to help you as best I can. If I ever forget to check back here as I sometimes do since not many posters are into pendulums, then feel free to p.m. me.
It was so nice to meet you and welcome to the forum.