Have your child place the music on the stand as soon as s/he comes home from a lesson. Have him/her open the music to the new assignment so that everything will be all ready to go when it's time to play.

Leave the violin and bow out during the week. Find a safe place (away from pets, babies, heat or drafts) where your child can leave the case open during the week with the violin and bow sitting inside set up and ready to play. The hardest part of getting down to practice is often opening up the case, rosining the bow, putting the shoulder rest on, etc. If the instrument is already set up, then all the musician has to do is pick up the violin and start playing.

Remind your child when it's a practice day. It would be so nice if we didn't have to remind our kids to do everything! My youngest daughter always needs a reminder to practice, but then she is reasonably happy to play through her lesson for the week. No reminder from me, however, means no practice from her. My oldest child is in middle school and her grade for orchestra is directly tied to her practice time (she is expected to do two hours per week). She doesn't need reminders to practice, but she does need to be reminded to practice the material for her private lesson.

Lavish praise. Tell your child when you hear something that you like—a piece, a passage, even an interesting sound. Or praise an attitude: “You didn’t really feel like practicing this afternoon, but you just went in and did it. Good for you!” I told my flutist once that I loved how she played Ravel’s “Sleeping Beauty.”  I notice that now she warms up with that piece whenever she practices.

Also, getting back to the instrument after a long break can be discouraging.  In those first couple of weeks, I find that a good dose of sympathy (“It’s hard to get back into the swing of things, isn’t it?") and encouragement (“Your fingers still remember that piece!”) go a long way. 

Attend concerts with your young musician. I find that students often make big strides on the instrument after hearing a concert. One of my young pupils from years ago had a very wishy-washy tone on the violin. After attending a violin performance, the student suddenly developed a lovely sound. When I asked him how he did it, he said that he heard how the soloist was playing and decided that he would play like that, too!

The Peninsula Youth Orchestra performs twice a year at Canada College. The California Youth Symphony, an excellent group of high school musicians, gives one or two performances a year at The San Mateo Performing Arts Center. And the San Francisco Symphony has an outstanding Family Series. 

Consider incentives. I offer my youngest daughter a treat after her lesson. We usually stop at a grocery store to get her a drink or an ice cream bar on the way home. This gives her something to look forward to on lesson day (which used to be a rather "dark" day for her when she was first learning to play) and helps alleviate some of the stress of performing for her teacher. By the end of last year, she needed a treat less and less frequently, and my expectation is that we won’t need to stop for one very often in the future. 

We frequently schedule special events such as television shows or videos or going out somewhere for “as soon as you’ve practiced.” Practicing seems to happen a lot quicker and with more enthusiasm.

We also offer one large reward for the entire year for doing a good job on homework and studies and for practicing 4 or 5 times a week without complaint. This has proved very successful in our family. When the going gets rough, I ask my young musicians what reward they are working towards. This seems to magically put everyone back on track!