Hi marieandtom. This might be seen by more people in a separate thread in General Knitting or How To. Just click on the Orange 'Start a new Thread' button.
But mostly it just takes practice to get the tension right with sts that are not too loose or too tight. With holes, you may be dropping stitches or accidentally wrapping the yarn around the needle and making a stitch, so count and see if you're adding stitches or losing them. A yarn over is done on purpose in lace knitting, but not something you want otherwise.
sue- knitting heretic