Run Chart

Hi All:

I have been in this field (six sigma) for around two years now, am still learning about the methodology & tools. Would really appreciate if all the knowledgeable people on this forum can help me with my questions.

Just saw this thread on Run chart, so wanted to clarify my doubts as well:

In Minitab the chart gives me information about four types of non-random behavior in my data, viz.

1. Cluster, 2. Mixtures, 3. Trends, & 4. Oscillations

My questions are:

a. If I don't look at the p value, how can I by just looking at the chart say that there is any one of the four non-random behavior in my data? How will a clustered data or mixture or trend or oscillation look like?

b. Is  there any rule / thumb rule about the number of data points to be used for run chart? If I am working on weekly data, how many weeks of data will I require. 

Is there any link from where I can get all this information. I have searched on google but nowhere did I get the detailed information.

Any help is highly appreciated.

Thanks,

Sam