Airbus Pilot - another trick is not to let yourself get too hot. Wear layers (if it is a chilly day outside) and let your instructor know if/when you need to remove one!
also ... an aerobatic pilot once told me ... when you are beginning steep turns (or any manoeuvre that you "feel" to start with) brace your stomach muscles, i.e. pull them in tight ... for aerobatics this is to keep the blood to the head, but for me in the early days when I felt unwell it made me feel I was taking charge of my situation!! whether it genuinely has an effect or not I don't know, but it wasn't long before I was fine.
I was extremely excited at the time to at last have the £££ to learn to fly so each lesson, in the beginning, was the height of this excitement as I suspect it might be for you too - this, plus natural anxiety (wanting to do well etc) plus concentration, plus being over-warm is pretty much a recipe for feeling unwell!
You will be fine very soon - promise!! Don't worry about feeling unwell and make sure you mention it to your instructor.
Oh and the other thing? suck Polo mints!! hehehehe