Hmmm ... from my experience, which is no where near "expert" status ... I think you'd have to frog back. (Hopefully, Ingy will be here soon to confirm or deny that!)
Have you heard about using a "life line" in your work? Generally, if you are doing something like a lace pattern, you place a life line @ the beginning of a pattern repeat. You just run some waste yarn through the first row of stitches -- you can even tape the waste yarn to your needle so that it gets pulled through as you knit. Then, if you have to frog, you can just pull out your needles & rip away, and you'll stop @ the waste yarn. Saves lots of time!!
Of course, you could always just leave it as is, do a different increase to get you to the right # of stitches (if necessary) and call it a Design Feature. Voila, you've made it your own! ;-)
If you realize that you have forgotten a YO, you can mark the place with a stitch marker and then on the next row just lift the bar of yarn between the stitches and put it over the needle and knit. If you have put one in where it does not belong just drop it off the needle on the next row. It will even out when it is blocked.
Thanks for your advice. I know about and have used life lines but right now I'm working on an afgan on circs. Also I know how to get rid of unwanted yos I don't know why I asked that. What has happened is I put the yo in the proper section but in the wrong place. So the counts okay it's just that the pattern is off. I wouldn't care too much if it were for me but it's a gift and I'm kind of anil about it.