Without knowing what mistakes you're making it's pretty impossible to say how to fix them. If you have dropped a stitch, that's fairly easily fixed with a chrochet hook. If you will look at the 'place' where the stitch should have been, you'll see a bunch of pieces of yarn, like rungs of a ladder, above where you can see the dropped stitch loop. Simply place the little loop that is your dropped stitch over the closest rung and pull the rung through with your hook, then do the same all the way up the ladder till you reach the knitting needle, where you will place the loop(dropped stitch). You can also purposefully drop a stitch and let it 'ladder down' to where you made some sort of a mistake...correct your error (stitch twisted? etc) and then go back up the ladder as above. This is with stockinette stitch knitting..if you've done some sort of a fancy pattern, then you'll need to go up the ladder using the stitch that should be on each row...if it's a purl stitch then put the slipped stitch loop behind the rung when you pull it through, to make a purl replacement rather than a knit. Hope this is understandable. I'd suggest you knit up a little swatch of a couple inches, purposfully drop a stitch, let it 'ladder down' an inch or so, and then practice picking it up. This is something you'll need to know how to do as we ALL drop stitches occasionally.

Sharon, I could have written your question. Everyone who learns to knit should also take a class in fixing errors because everyone makes them. You are so right--crochet is easy to unravel and fix, but not so for knitting.

I often knit backwards, taking out stitch by stitch until I reach the error. You have to be careful not to twist stitches doing this. Or I've even pulled the needle out, unraveled past the error, and then using a smaller needle re-insert it into the stitches. Practice makes perfect, and believe me, I've had a LOT of practice! LOL!

I saw three books on Amazon recently, and I was thinking of getting one for myself:

Knit Fix
The Knitting Answer Book
When Bad Things Happen to Good Knitters

It is easy to just unravel the one stitch if you see that a few rows down you purled when you should have knit or vice versa, or the yarn split so that a ply of the yarn is hanging loose. Just follow Sandra's complete explanation. I bet knittinghelp.com has a video to demonstrate it.