This post is most definitely a personal opinion that reflects my particular experience and clientele. I am interested in comments as to whether you agree or not with my thoughts!
Although I try as hard as I can to stay current with the technology of business appraisal – how we do things – I have found that there are many analytical procedures that I just do not have occasion to use at all, or very infrequently.
Under the Income Approach, I have posted extensively as to why I do not use WACC (the weighted average cost of capital). The overriding reason is that I can always come up with explicit assumptions for the level of debt a subject company will owe each year (in a multi-period forecast), so I can always calculate cash flow to equity and value it directly.
Closely related to that, I use the multi-period discounting model rather than the single-period one, because for every engagement in which I need to develop a financial forecast, I do a multi-period one.
In those forecasts, I do not use the mid-year discounting convention because the uncertainty associated with the forecast amounts dwarfs the size of the conventional adjustment.
Moreover, I use the build-up method to develop discount rates, and not CAPM, in which the problem of estimating volatility for a small private company is huge.
Considering the Market Approach, I have not had occasion to value a subject company using public guidelines or transactions simply because the vast majority of the subjects are too small to be compared to public companies. For the few that are larger, they have all been financial reporting related assignments (e.g. 141-142 or 718 (formerly 123R)) in which the company was owned and independently valued by a private equity fund. The fund used public companies and transactions to value its subject; I merely confirmed that what they did was reasonable.
Also under the Market Approach, when I use the Direct Market Data Method I rarely (maybe once in every ten or more assignments) have a large enough sample of guideline companies to use any sort of statistical analysis (such as regression).
Under the Asset Approach, I have not had occasion to use the Asset Accumulation Method (in which all individual tangible and intangible assets are identified and separately valued) except in the occasional 141 or 142 assignment. For all the rest, this method is extremely time-consuming and expensive, and better and easier results are obtained by the Market and Income Approaches, which do not break out these values (and for which there is no need to do so).
With regard to discounts for lack of control, I do not use market studies to determine control premiums and values; I look at the individual control prerogatives and their cash flow benefits and quantify the effect on cash flow. I do use them as a high-end limit (the low end being closed end fund discounts) when I benchmark them.
For option-related valuations, I have come to rely on the binomial model rather than Black-Scholes because it is less restrictive. (The reasons for this are very technical, but if you use the BVR 123R model developed by Derivative Value Associates, they include a great explanation of this in their documentation.)
By the same token, I do not use the option-related models for quantifying the lack of marketability discount because their output ranges are so wide: I get narrower and better results by benchmarking and double-checking with the QMDM.