How to Truly Differentiate from your Competition?

Do you keep hearing - "You sound just like the other guys who were here last week"?

It can be hard to keep sounding different from your competitor.
Why should you differentiate from your competition?

It will help drive more value and avoid competing just on price.
It can make your customers identify better with you
You will be remembered more and more likely to be called back.

However this can be hard to do.

How do you sound different from the competitor? Do you sound like a clone?
Competitors or Clones?

First up - there could be a case for copying your competitor in some ways - "When is it OK to copy your competitors" describes a few ways that it is - and isn't - ok to copy them. These include improving on what they do, and also "drafting" in their slipstream can help you get something out of the noise they create in the market.  However these methods also imply differentiation as well.

Sometime the language you use is identical to theirs.  We had a marketing campaign recently where we actually coined a new phrase to define our competitive advantage, and about a year later, the main analyst and then all our competitors starting using the same term.  Watch out for using too many buzzwords or jargon terms, as these will quickly lump you into the same category as them.  "Stop Talking Like Your Competitors"

The other thing is - the competitor may have a flawed business strategy, and by following the herd, you might end up in a place you don't want to be either.
They could be giving away a vital part of their product, or focusing on the wrong segment, or even just building the wrong features for the future.  Either way, by following them, you make your pitch, product and strategy sound the same as theirs and end up in the wrong place.  This article "Stop Copying Your Competitors: They Don’t Know What They’re Doing Either" talks through some of the pitfalls in following your competitor's strategy

What you should do?  
Work out your key strengths, what they mean to your customer, and express them using language that will sound like a breath of fresh air.