Here are a few miscellaneous tips on problems, stitching techniques, and changing yarn colors within a project. Again, there are easy to follow illustration this page:
Difficulty pulling hook through loops (Split stitches)
It is easier to pull yarn through loops if the hook is turned slightly down with yarn pulled firmly around the hook. The yarn must be loosened after each stitch is made.
Turning chains - what are they and do they count as a stitch
Turning chains are the number of chain stitches worked at the end of a row to achieve the required height for the next row.
Working Under Front, Back or Both Loop(s)
Generally a crochet stitch is made by slipping the hook under the top two loops of a stitch, but some patterns will say to insert the hook through the back or front loop only. This creates a ridge or horizontal bar across the row. See Crochet Abbreviations for working into the front or back loops.
Working around the post
Post refers to the stitch below the row being working. You literally circle the post of the crochet stitch below, either from the front and out again or from the back and out again and then work the stitch as usual. This produces a raised effect.
Changing yarn colors or starting a new ball or skein of yarn
If you are simply joining a new ball or skein of yarn in the same color, it's best to do it at the beginning of a row because it is easier to hide the tail of the yarn. Simply wrap the new yarn around the hook and draw up a loop and continue crocheting. Leave a 6" long tail of yarn to, tie a loose knot to hold the yarn in place. When you complete your project, untie the knot and weave in the ends. This also applies when you have to change yarn in the middle of a row.
When a pattern says to change colors, it is made this way: Work the last stitch to final two loops on the hook, draw up a loop with the new color and complete the stitch. If you are following a color chart or crocheting a multicolor pattern, yarn can be carried along the back of the work if the repeat is fairly close together. If yarn is carried more than 3 or 4 stitches, carried yarn should be caught into the work every 2 or 3 stitches.