I'm using SITD to quilt the top in my avatar. Its got a plain backing and is looking quite good. Two questions:
What's the best way to finish a row of stitching so that it looks as neat as possible on the back?
I'm using clear thread on top: not too bad, as I'm using the Superior one, which causes fewer problems than some of these do, but even so, not great. I'm wondering - if I'd used ordinary coloured thread, what colour(s) could I have chosen for a top that has a mix of colours like this one?

Depends on whether you want the stitching to stand out. I would probably have used a soft gray.:)

I think I would too!

I try and use a thread that matches the back. With SID in the front you shouldn't see your stitiches or hopefully very few of them. So the back is what matters to me. That said, I'd find one that blends well with both your top and back fabrics. If you're using clear thread on the top are you able to use it in the bobbin also? I have never had any luck with clear threads as they drive me nuts.

When I start or end going around a block. I start with pull up my bobbin thread from the back, sew what I need to, then stop and bring up bobbin thread. When I'm done with the top I go back and tie tiny little knots and clip threads.

That way no backstitches showing on the back.

As far as the color of thread, it all depends on what you want. You could match your thread to the piece color of the side that you're SITD'ing. Use an accent color, I can see a black would look cool.

I'm not that great at SITD yet, and I have to confess to more stitiches showing than should do! Which is why I used clear thread on top. It's not behaving too badly, but even so, I don't really want to use it again unless really necessary. I'm not using it in the bobbin - I suspect my machine would throw a tantrum if I tried! And I would worry about it getting into the works.

I finish a row and then knot it and bury the threads. If you are going to show a quilt then this way is the best. You could also use mono philament clear or smoke..

That's it! That's the method someone taught me that I couldn't quite remember. Can I just check - I've just done it by bringing the quilt a little away from the needle, cut the threads then using a pin in the final stitch to coax the bottom thread through.

It's the mono filament clear that I'm using. Softer than a lot of these threads and doesn't break TOO often, but I'm awfully fed-up with rethreading the machine because the thread's bounced itself out of place again.

When you SID are you trying to slightly pull apart the ditch part so you end up in the middle (of the ditch)? Also if some of your stitching shows it's no big deal - truly you could be going along absolutely perfectly for a bit and then for whatever reason it will show up. It just takes a lot of practice so don't be hard on yourself...one day you will just find you have no problems at all. Just go slower than normal and really watch your fabric and how it is behaving. I fought that darn clear/darker clear type thread for what seemed like an eternity to me. My machine didn't like it and I despised it. So what works for some is a nightmare for others. You will get there so be patient with yourself and don't be so critical. Remember what you can see others rarely see what you would call a boo boo. We only learn with practice and our mistakes....then we get the OMG moment and everything just works how it's supposed to and although we queston our sanity at times we are all so excited that we finally got it. We've all been there, still going there in different situations but the joy of figuring out the problem far outweighs the frustrations along the way.