I recommend tacking (or basting) your seams with Gutermann tacking thread. As you know, tacking or basting is when you sew together the layers of material by hand first, with long and even stitches, ready for stitching by machine. Use a long, hand sewing needle, with a large eye. Yes, it seems to take a little extra time, but it actually saves time overall. Otherwise, those pesky seams can move just a little while you are machining your seams and then you have to do it all again. I never put in a zip without securing it first with a tacking thread and I never have a problem.
What is so different about using a special thread? Well, this tacking thread by Gutermann can be pulled out easily afterwards without harming your fabric. Remember to pick a colour which will stand out on your fabric, so that it is easy to find and remove afterwards. There are three shades available.