It is difficult to put a general rule but broadly I can illustrate what I do in financial analysis:
1) The business comes first as a scalable/non cyclical venture assumes greater sustainability of earnings and lesser chances of movement away from the linear path.
2) The RoCE should be equal to or greater then growth if the RoCE is low then we need to understand whethre this is low because of investments that have been tied up in initiatives that are not yet contributing to bottomline or this is the historic trend all along.For example if LT has a 40%+ RoCE we need to see if this was the trend say 4 years back or are they in a sweet spot. With HDFC ban they have maintained a ratio of 20% all throughout.
3) PE should be equated with growth where "growth" will be capped at RoE => normally. COmpanies talk abo9ut 70% growth with a 25% RoE. This is amathematical impossibility in the long run. In the short term 2-3 years you can have 70% growth by improving efficiencies.
4) Margins do not matter. What matters is industry margins and whether the company has got the best margins in the industry. For example company with 30% EBIDTA and 20% RoE is worse then a company with 10% margin and 20%RoE. That is because with a 30% EBISTA new competitors will get in to break the entry barrier thus driving margins down!
5) I look at the industry size. For example a company with a market cap of Rs 1000 crores in a Rs 10,000 crore industry is approaching saturation compared to a company with a 10,000 crore market cap with a market size of Rs 500,000 crores! Market caps in absolute nukbers are misleading and mean nothing.
Now about valuing stocks as part of case studies what I do is put these parameters along with a few other normal ones like mktcap/sales etc for the various players in an industry.
It is diffcult and almost impossible to target an absolute price for a stock. What we get is broad approximation as to whether a stock is overvalued or undervalued and then we take it from there.
Maybe other people can add to this and we can take that forward.