Leg 'cues'

I'm not sure how to explain this precisely, but I'll give it my best shot. Rainy is 5, had only had 30 days training when I got her, and then it was just me and my instructor doing our best. She's definitely come far, but now that we're past her bucking tantrums and she's started to listen more often, I've been trying to effectively use my legs to steer and control her. My problem is she doesn't respond to what I'm doing. I don't know if it's me or her- I assume me, because 99% of the time, it's the rider's fault, so I'm trying to get advice. If it's too complicated to explain here, what should I ask my instructor about, and/or are there any good books that would help? Also, on the offhand chance that it is Rainy, what can be done? Thanks in advance.

Is your leg in the right spot on the horse's body?
Are you giving the cue at the right moment?
Are you making the cue clear (not wobble wobble press, but a distinct, firm pressure)?
Has the horse has been trained to understand the cue?
Are you restricting her with your hands or seat while giving the cue with your leg?

Make sure your leg is int he right spot, touching the horse correctly where it should be. And be sure you are "Opening" the other door of the inside leg.

Maybe you should go back to groundwork for a little while and just do the basics. Is she responding well fromt he ground?

She does listen on the ground- my one thing is that she might not be trained to respond to it- I don't actually know what sort of training she had. If so, how would I go about training her to respond? I think I'm asking correctly, but I'm planning on asking my instructor next lesson (Monday).

If you are the one that has done most of her training and you haven't trained her to repond to leg cues then she most certainly won't respond to them. I won't even try to explain how to ask for them here. What you should do is find someone that is qualified to help you understand how to train her to respond to your legs. If you know an experienced horseman that will help you for free then all the better but if not then go to a GOOD horse trainer (not a coach or riding instructor) and get some help from them. You should have been training with leg cues since the first ride so that makes me think that your instructor doesn't know much more than you do.

Make sure you're not trying to work on the leg aids and the mouth aids at the same time. Everything must be established from the leg before you even think about taking more than a feather-light, following contact. Your horse sounds very green, and like she needs to just work on the basics. I suggest picking up some dressage books - Training the Young Event Horse (great dressage section) by Pippa Funnell, The USDF Guide to Dressage, and The Elements of Dressage by K.A. Von Ziegner are all good. Oh, and Common Sense Dressage by Sally O'Connor.

Thanks! I'll be sure to check those out- she is awfully green. :P