It's easy to be tempted by all the pretty, unique, soft yarns out there, but the truth is that the first couple of things you knit are not going to be worth the nice yarn. Besides, it's gentler on your wallet to start off cheap and then move onto the luxurious stuff when you know you can do it some justice.
What do I mean by plain yarn? No loopy yarn, no furry yarn, no bulky yarn. You're going to want to pick up a skein of 100% acrylic worsted weight yarn. You can find the information on the yarn label itself; the fiber contents will read "100% acrylic" or something similar, and a little picture of a yarn ball should have the number 4 on it, which signifies that the yarn is worsted weight, or medium weight. This is the most common yarn weight. Red Heart Super Saver yarn in your favorite color is a great, cheap, easy place to start.
Needles aren't like yarn where you can use them up. Your needles need to carry you through all of your future projects, and therefore should be sturdy and comfortable. In an ideal world, you could go to your local yarn store and ask to hold a few pairs of needles in your hands before deciding on the brand and material you prefer, but if you don't have access to anything like that, we recommend size 8 single-pointed bamboo needles.
My personal needle preference is aluminum, because I like it when the yarn can easily slip off of the needles, but that's dangerous territory to be in when you're a beginner and you're dropping stitches like hot cakes.
Here's the key: once you've decided whether or not you like this pair of size 8 bamboo needles (preferably after knitting your first swatch), and you've decided that you like knitting and want to keep going, spring for an interchangeable needle set. These sets are a bunch of needle tips with cords that connect them. Technically, they are all circular needles, but a fun tip I learned early on in my knitting career is that you can knit flat on circular needles! Many people find them easier to hold than single-pointed needles, as well. Choose a set of bamboo interchangeable needles if you liked your first pair, or aluminum if you did not. Now, you'll have every knitting needle size under the sun to play with in your future endeavors, and you'll only need to worry about double-pointed needles... but we won't get into that now.
If you're learning to knit in modern day America, you're typically learning one of two styles out of many: English or Continental. Personally, I learned English style: in this technique, you hold your yarn in your right hand as you knit, and pause to wrap it around your working needle each stitch.
With Continental style, by contrast, you hold the yarn in your left hand and "scoop" at it with your right needle. If there are any crocheters reading this article, this may sound familiar, and it's true: it's often easier for crocheters to learn how to knit Continental style rather than English.
Why do I recommend you learn how to knit Continental? Continental style is faster and (arguably) easier on your joints. If you've already learned to knit English style, that is fine, and you can either switch things up and learn to knit Continental or just keep merrily knitting English style. There's no rule here, but I wish I'd learned to knit Continental style, because now I have trouble learning any style of knitting other than English, and I'm a real slowpoke when it comes to my knitting.
Many instructors begin with teaching their pupils how to cast on with the much-more-often-used longtail cast on method. We do recommend trying out the longtail cast on method before all else, but if you find it just confuses and frustrates you, try learning the knit cast on method instead!
This is the cast on method I personally learned with, and while I never use it anymore, it was insanely helpeful to me in the beginning. While this cast on method isn't usually specifically called for in a pattern (but can certainly be used if no other method is specifically called for), it's simpler to get the hang of, and teaches you both how to cast on and how to complete a knit stitch in one. This may not make much sense to you yet, but after you've cast on and you start learning how to knit a stitch, you'll find that you've already learned how to do this, minus one small step.
Now, you have your yarn, needles, and a grand idea of the very first scarf you'll knit, but I'm here to hold up the "yield" sign in your face and recommend that you start off a bit smaller. Rather than jumping right into a scarf, knit up a swatch instead: that is, when you learn how to cast on and knit, just knit a small square of fabric in garter stitch (psst... garter stitch is simply knitting every stitch)! This way, you can address any issues you encounter without worrying about ruining a lovely scarf or, heaven forbid, a gift for a friend.
I jumped straight into a scarf myself, and I don't even wear it to this day because the beginning is just so hideous. That's because I hadn't quite perfected my knit stitch yet. This brings us to tip #6.
Knitting tension is something even seasoned knitters (like myself!) struggle with to this day, but not quite to the same magnitude as beginning knitters. You'll find that your rows are drastically uneven, your stitches seem to be hanging at the edges, and your swatch looks more like a piece of mesh than a sample of fabric.
Mark my words: you will grow out of this. Be like Dory from Finding Nemo and just keep swimming... er, knitting. Keep working on your swatch, and continue to knit onward until you see your stitches start to even up. Learning how to even up your tension truly comes down to understanding how tightly you should be wrapping your yarn, which is something you can only learn through feeling and practicing. Heck, you may even find that you're no longer adding or subtracting random stitches anymore by the time you've knit up a few inches!