My theory is if it can't be seen on a galloping horse from forty feet it is ok. That goes for SID, getting corners to always match and perfect points. Just enjoy the process and the fabrics. Don't get upset if all is not perfect. You will enjoy it all the more. Strive for your best but don't sweat the small stuff.

From what I've read, using a SID foot with the metal guide running precisely along the stitching line puts the stitching just to the right of the seamline, which is correct. According to SID info., if you stitch exactly on your stitches, it weakens the seamline stitching; therefore the stitches SHOULD be just to the right of the seam. My SID foot works that way. (IMO, without a SID foot/metal guide, it would be virtually impossible to stitch a straight line next to the seamline.) If you have the SID foot and still sew crookedly, one thing you need to be careful about is sewing over "lumps" where two seams meet. Those lumps can cause your guide and stitching to go wonky. Also, when using the SID foot, the narrowest zigzag stitch works well.

I have found that using a walking foot works best for me for SID. Also sssllloooowwwwww dddoooowwwwnnnnn. I always think there is a race going on and I have to be first. I learned to slow down a lot when SID.

I have tried the SID foot, all it did was get hung up on the thread in the ditch.

I go for the 1/8" next to the seam..I also like to echo quilt when the pattern is appropriate for it, that way I can use my 1/4" foot as well....

I orderd a SID foot and hope to get it soon. I am lousy at FMQ. Is meandering different from FMQ?

It really helps when the seams all lay to one side or the other. When the seams flip from block to block, the foot has a tendency to jump the ditch (so-to-speak).
It also helps to make sure that your sandwich is pretty taught. That helps control the sides with your hands.
I roll my quilt into a tube and guide it through the throat. Sometimes, it gets very heavy and is hard to control. Sometimes, the sheer weight of it pulls the sewing piece out of whack. Take rests.
Lastly, go slow.

Thank you one and all for your suggestions. You've given me wonderful information :D

Meandering is FMQ. So is stippling (smaller loops, etc., than meandering ... much more dense stitching) and, in fact, any design that you create while your machine feed dogs are down and you are guiding the machine while it stitches is FMQ. Flowers, leaves, feathers ... all take practice but can be done free motion. I can do meandering and stippling and simple leaves & vines o.k., but if I try to FMQ anything very complex, it looks like I'm high on drugs and/or booze ... it is quite frightening looking and not at all attractive.

I forogt to tell you that I don't relly SID - I MAD (meander around the ditch) lol. If I have more than one glass of wine, it is FID (fall in ditch).

Here's my secret. I don't do SITD anymore. That's how I solved the running-all-over-the-place problem with it! It's just too fussy a technique for me, especially since I get too perfectionistic about it.