Good evening! I introduced myself on the Welcome… thread but have a few questions I thought I’d post here. I am new to knitting - in fact I haven’t even started! I have no idea what I should buy. It looks like there are different sized needles? What about yarn? Do I just buy any old yarn to practice on? I did find one site, Learn to Knit, where you make a 7x9 rectangle then send it to Warm Up America. They say to use worsted-weight yarn (will it say that on the package?) and size 8, 14"-long knitting needles. Is that pretty standard? Any thoughts on how to get started and what to purchase would be greatly appreciated!
New to Knitting w/ Questions
Welcome to your new addiction! 
I would suggest just a simple worsted weight yarn, nothing furry or feathery, and yes, it will say worsted on the label. A size 8 metal needle is good to practice with, too.
There are a billion yarns to choose from down the line, and a wide range of needle sizes, but if you start with the basics, you’ll learn best.
With the videos and people here, you can’t go wrong!
Awesome - ty! I am anxious to get started!
Hi and welcome.
I would recommend that you start with circulars. I just tried circulars for the 1st time in November when a pattern I was using called for circulars as well as straights. I purchased Susan Bates Silvalume 24" circulars and they are a joy to work with even for flat work. If you decide to stay with straights, the 10 inch length is more comfortable to knit with.
Ben Franklin stores have the best selection of Susan Bates circular needles.