I have been handquilting for 40 years. Everyone's advice so far has been great. I have used everykind of thread at one time or another. I learned the hard way not to cut more than a arm's length of thread at a time. When you handquilt you literally drag that length of thread through the fabric everytime you take a stitch. If you cut it longer it not only tangles easily but it gets frayed and may even break. One trick is to always thread the needle with the end of the thread that is coming off of the spool. It has something to do with how the thread is spun. I usually use the same color thread all over the quilt. Sometimes I get creative and use different colors on different colored areas on the top. This only works well on the back if it is an overall print that hides the different thread colors. Recently we used a multicolored thread meant for machine quilting on a quilt we were handquilting at the senior center. It was a stack and wack star block made with bright batiks and sashed in black. The quilting we did in the black areas really looked fantastic.
Good luck and happy quilting.