How to Read Crochet Patterns: Check The Header
The Header of a crochet pattern is the part before the Instructions.
The Header contains the information about the STUFF that you need in order to make the project.
The Header includes the Photo, which tells you what your project should look like when it is done (click on the link to get more information about what you can learn from the project's photo). And if you look closely at the photo (assuming that the photo is reasonably clear), it will indicate what kinds of stitches are used in the project.
Read Crochet Patterns: Difficulty Level
If you're a crochet beginner, this symbol (or an equivalent) is really important.
Skill Level 2 - Easy
This particular symbol is saying that on a scale of 1-4 (Beginner, Easy, Intermediate, Advanced), this project is considered a 2 (Easy).
If you have just taken crochet lessons, try to find patterns that are Level 1, or Beginner. Beginner patterns in general don't have any shaping - you will make rectangles, like scarves or dishcloths or afghans. You will probably just be doing back-and-forth rows of the same stitch.
If you have someone to call on for help, you could probably do a Level 2, or Easy pattern. These patterns are more interesting than back-and-forth rows of the same stitch. You might be doing rounds instead of rows. There might be increases and/or decreases. But the patterns will not be too complex.
The Intermediate and Advanced patterns are usually much more interesting! If you are new to reading crochet patterns, you might want to get some more practice before attempting one of those patterns.
Read Crochet Patterns: Yarn
Most crochet patterns will tell you to get a specific brand and label of yarn - a lot of yarn manufacturers provide patterns or sponsor pattern designers.
Some crochet patterns will tell you to get a particular weight of yarn (such as lace, super-fine, fine, light, medium, bulky, super-bulky).
In many cases, you will a symbol such as the following, for medium weight yarn (also called "worsted"):
Yarn Symbol - 4 - Medium
The most common question that beginners have is "Do I have to use that particular yarn?". The answer, as usual, is "It depends!".
It all comes down to the Gauge (click on the link to get more information about Gauge). You can use whatever yarn and hook you want to, as long as you work to the specified gauge.
In general, though, you should use a yarn of the same general weight as the specified yarn. So if the pattern writer asks for a #4 or medium yarn, use that weight of yarn.
But beware - not all yarns of the same weight work up to the same gauge! You might still have to play with it to get the correct gauge.
Read Crochet Patterns: Hook
The crochet pattern will specify a hook size. Sometimes it will specify more than one.
On a good day, the hook size that the pattern writer specifies will be the same as is suggested on the label of the yarn (unless the pattern writer is trying to achieve a particular effect).
Warning: there are several standards for hook sizes. You need to know, at the very least, the country of origin of your pattern, and even perhaps when the pattern was printed. It is best when the pattern writer specifies the hook size in millimeters - that eliminates any confusion.
Here is a handy chart from the folks at Coats and Clark.
Hook Sizes
Another warning: most patterns will specify a particular hook size, and then add the phrase "or size needed to produce gauge". See the Gauge article for more info on this.
Read Crochet Patterns: Other Materials
If anything else is needed (like stitch markers, buttons or other notions), they will be included in the Header of the crochet pattern.
Conclusion
If you have a burning desire to make something from a crochet pattern, your first step should be to get ALL of the items specified in the Materials list. But trust me, you still should not start the project until you have created a gauge swatch, as described in the Gauge article - because you may need to use a different hook than was specified in the Materials list.
