Numi, I’m forgetting (or maybe never knew), what LTM is, and TTM. Can you refresh?
YP, my sense on EV/EBITDA is that EBITDA is something readily available from recent financial statements or accounting equivalents (in the case of a non-public company). Then you take a look at total enterprise value (Value of Debt + Value of Equity - Cash) per $ of EBITDA for comparable companies in the market place and come up with an average ratio for the industry.
From there you figure out an EV target value for your company by using known EBITDA and multiplying by the industry average EV/EBITDA, then adjust (subjectively or using some other model you like) to account for whether you think the company is above average or below average relative to the comparables. You may then subtract known debt obligations to come up with an equity value, or just keep the EV value there if you are going to buy the whole shebang.
EBITDA is used to as a crude measure of free cash flow. If you have EV/FCF multiples, they should work better in theory (though others on this board probably have more practical experience about how well they work or don’t work). My guess is that in PE, the winning deals usually have a sufficient margin of safety that EBITDA vs FCF doesn’t make so much of a difference as to make it worth the extra effort in computation, but I may be wrong on that.