Awww...congrats!!! I just recently went through my girl having her first litter!
I think the signs of labor that I noticed were scratching and digging in the litter box a few days before. She also loved her tummy rubbed
She was a little restless and started digging in her nesting box. I knew she was in hard labor when she was laying in her nesting box, and started putting her butt in the air (almost like she had to poo) every now and then. After a bit (maybe 3-4 hours) she popped the first baby out!!
A few things I found helpful were to have all of your supplies handy and ready to go, have dental floss pre-cut in case you need to tie the cords. One thing another breeder told me was that after she had the first few kittens, give her a mixture of plain (not low fat!) yogurt mixed with a little warm water and a wee bit of Karo (corn) syrup (through a syringe). It will give the queen an extra boost to get the last one or two out, and help prevent uterine inertia (what I was told). My girl took it with no problems, then pushed out the last one shortly after.
I also had a snuggle safe warmed and ready to put the babies on in case they needed it if they came too fast for her to keep up with.
There is a great thread in the breeding section that has tons of info regarding supplies.
I am sure you will do fine with your litter! The waiting is the hardest part
Best of luck to you and your future babies and congrats!!!!