OK - these seem to be the answers I have figured out so far from my little life of mine. I am sort of shy - but once I warm up, I often get told to shut up. lol.
If your with someone who is giving one word answers - then do not worry. Yes, its damn annoying though! Forget verbal confirmation of the old "does he/she like me" - its the body language that gives u the answer.
If your chatting away and they are looking around for an escape route - its obvious they have other things on their mind than you (give up basically). If their body is pointing towards you, then its likely to mean that they want to engage with you - simple. This does not mean however, that just cos someone turns away for a few mins, that they hate you. lol. Thats likely to be due to them being uncomfortable so they have to repositon themselves.
I find that the best way to do it (if you have enough courage), is to show more physical things to that shy person. Like dont have your hands on your lap whilst talking - move them about and possibly touch the shy persons hands briefly (not often enough so you grope them or come across like your an odd job).
If you keep getting one word answers, ask more personal questions like: "so, what hobbies do you have", "o, that sounds cool - how did you get into that. How good are you at it", "How often do you do your hobby", etc. This will make the shy person feel like you are willing to give up your time in order to listen to them. Hence this will make them relax more due to them being made to feel that little bit more special and unique.
If the person keeps chatting to others (a lot) rather than you - then they simply arent shy - they arent interested. Simple. Its up to you to keep them interested though, by asking interesting questions.
Me being shy can tell you girls this: when it comes to physical contact, I just lock up and freeze. This then in turn makes it seem like I dont like the person, when infact its the opposite - I dont wanna screw up so much that nothing happens. Its all in my head. If I knew someone was taking a real interest in me - Id be much more likely to make a move, or at least show some "I like you" signs.
Also, please dont take the first impression that this is how someone is always going to be - takes a good few hours (or days or weeks) for some people to open up. If you like that person - stick at it and they'll think to themselves and acknowledge your putting in a lot of effort (though dont get taken for a ride).
Basically - find the key to what makes them tick. Once you have that, keep adding to it and then voila!
Thanks for reading my ramblings.