http://www.knittinghelp.com/videos/knitting-tips
Near the bottom of this page is a video of picking up stitches.
The main thing is you want to pick up enough evenly spaced that the item still lays flat. so maybe you might need 6 where they tell you 5, then that is OK. Don't try to force it to 5. So when they tell me to pick up X stitches, I consider that just a guideline, I may need more or fewer.
Also to consider is what stitch pattern are you using from there? ie, if you'll be doing ribbing 2k, 2p, make sure you end up with a multiple of 4. Maybe you needed to pick up XX stitches and have an extra stitch (from the multiple of 4) -then I would just stick in a k2tog in the next row, somewhere where it won't show, maybe the back of the neck.
You can also search youtube.com for 'knitting pick up stitches' for some more. Sometimes it takes a couple different people showing you to get it.