I was a new cat owner two years ago and not knowing what to expect I made a couple boo-boos...
One, I don't have doors that shut properly except the bathroom in the house... so I let him out and it was too overwhelming with all the space... use one room to introduce him to the house, give him/her to get used to you, and go from there... my mistake took a while to remedy because he was a scaredy cat (which I knew before hand)
Second, I kind of expected him to love me instantly... again, so not the case, do things on the cat's pace, in the cat's comfort zone, don't try to pet if it's skittish at first, don't approach it, let it come to you. I kept trying to lure my guy out and it would just send him into deeper hiding (to the point where I had a hard time finding him)
Thankfully, I picked up on my mistakes fast and let up quickly and realized he would come out and check me out and sit and watch and all that if I just let him be... and I worked it out.
Most of all, enjoy getting to know your new addition... that's the best part, once you earn their trust and love there's nothing like it, they're great companions