I've been thinking about all the valuable bits of information that aren't necessarily in the manuals. The manual guides you step-by-step through making ribbings, but it doesn't necessarily say WHY you must do this or that. Here are some examples:
1. The ribbing can easily be too loose for the garment. It might seem logical, that if my garment is on a 7 tension, my ribbing could be, say set on 5 - that is, if you are thinking of hand knitting needle sizes. However, you really need a swatch of your ribbing before you begin, and you need to make it tighter than you'd probably expect. Why? The gap between the ribber and the main bed adds some distance that the yarn must travel between each knitted and purled stitch, and that distance adds to the size of the stitches.
2. Weighting work on the ribber is quite different from weighting work on the main bed. I might use two claw weights on a good-sized width of fabric on the main bed and all is well, because the fabric presser does a lot of the job of pulling the work down so stitches knit through. On the ribber, though, the ribber arm doesn't have wheels and brushes, so you depend on gravity. Get used to the idea of using more weight.
3. It's very important to balance the comb, but isn't it a contortion getting the comb in there correctly? Mark the center of your ribber comb with bright nail polish (why should the sock machine folks get all the nail polish uses?) and put that at zero, the center. Put your comb in between the beds with the wire in it, bring up one side and slide the wire almost out, then slide it back in with the teeth in place between the stitches. Whew. Much easier!
4. In my experience, circular knitting takes the most weight. Keep an eye on circular knitting and make sure the stitches are knitting through.
5. When you added a ribber to your 200 needle machine, suddenly you had 400 needles! That means that you can do a technique called "full needle rib" which uses every needle in a knit one, purl one configuration. Please bear in mind that for this technique and for other techniques which have the needles closer together than the usual 4.5 millimeters that you must use much thinner yarn.
6. Did you know that the medium comb with the brass bar can be used as a "buckle" for weighting the work when it gets too long and hits the floor? You remove the ribber wire, insert the knitting between the brass bar and the comb so that weight will make it stick (sort of backwards - I guess I better do a video), and then hang the weights. You can slide the comb up as you work, gathering the width of the fabric into the comb.
7. I talk about this in my videos, but there are certain items you'll use constantly if you add them to your ribber equipment. Get some spare weights and some triangle weight hangers, either from a dealer or second-hand from a knitter. Sometimes you can find a short ribber comb, and if you can't, you can usually purchase a long ribber comb and cut it into a short and a longer-than-medium comb. I like to have spare double-eyed needles, too.
8. Experiment with your fine knit bar! This is a long white plastic strip (lurking in the white styrofoam packaging - I've heard of folks discarding it because they didn't even see it). It goes between the main bed gate pegs and the bottom of the needles and is wonderful for getting the stitches to knit through. You won't always use it, but it will often be a real help.
9. If you carry your ribber around or have to store it, a plastic shotgun case is a fantastic, cheap solution.
10. Ribbers can get out of adjustment. First of all, make sure the brackets are inserted correctly in the back of the ribber bed and also attached correctly to the main bed. Make sure the needles match up between the beds, that is, full pitch matches and half-pitch has the needles halfway in-between each other.
11. Ribbers often have sponge bars, which wear out and need replaced.
Okay, commenters, what else just isn't in the manuals and ought to be?