fitting.... hmmm...

There are lots of guys who can fit you (they use lots of gadgets to do this) with years of experinece.

I have not tried using this devices yet, but here's what i learned..

Find a bike that really fits you well(the one that you are comfortable of riding at your own pace). Use that bike as a benchmark for your choices..

Measure the Toptube, Seattube, Stays, Wheelbase, stem, etc....

Also measure the "reach" (saddle - center of handlebar --- i think this should take care of the seattube and headtube angle issues) and standover height.

Just bring a steel tape when you shop for a new bike/frame and measure..
Please take note that 54cm size from one manufacturer might not be exactly the same on another. So let this be your guide(It is mine BTW).