Both my husband and I have advanced degrees in engineering. We value math education. I have been very concerned about the inconsistency and quality in public school math curriculum, so I take the responsibility on my own to make sure my kids learn a solid foundation.
When they were at elementary school, they did the Highline advanced math program at http://home.blarg.net/~math/. The two-year program is effective to practice basic skills in all areas. In addition, I purchased contest books from http://www.mathleague.com/. These books offer challenging multi-choices questions.
If a student is serious about math, I suggest she or he accelerate through all middle school and high school math curriculum. My older son took EPGY math from Stanford gifted program http://epgy.stanford.edu/ and finished precalculus around 8th grade. He got a good foundation and that really counts. I wished he had taken Geometry too but somehow we did not do it.
In addition, both of my kids visit http://www.artofproblemsolving.com/ website. The website publishes a two-volume book called "The art of problem solving". The book is geared toward AMC competitions. My friend's son Jonathan Hung, a 8th grader, worked through both volumes. It was frustrating at the beginning because of the depth, but he worked very hard and overcome the challenges. He placed 1st at Washington State Math Competition this year and also made it to the Washington State MathCounts team. The team finished 2nd place at the National and Johnathan placed 29th among 228 finalists. I can take some credit in his success because I introduced the website and books to him :).
To really excel, a love of mathematics is needed. It is more important to foster that passion so the child will work on problems by her or himself without parent supervision. Luckily, this is the case at my house. My older son has been a USAMO qualifier for two years and my younger son was invited AIME this year at 7th grade. They both think math is their favorite subject and are happy with what they have learned. It is very rewarding to know that the mathematical seeds I planted in them have been growing steadily and lively.