Here's what I hope has happened if you're learning about ornamentation from this site. You started by reading the section on articulations, then you closed your browser, turned off your computer, sold your television, quit your day job, and went away and worked diligently for a year or so on getting your cuts and taps nice and clean and precise. Then you came back, turned your computer on again, and carefully read the next section on rolls and cranns, then went away and worked on those for, oh, say two years. Then, you blew the dust off your computer, booted up one more time, and read the third section. You picked maybe two or three techniques that you thought sounded interesting, and began working on those. You're starting to think about finding a part-time job, something that won't interfere too much with your practicing.
For the occasional flute player who hasn't followed this course of study (I'm sure there are one or two), here are some things to keep in mind.
Playing with good solid rhythm is the most important thing to learn in Irish music. Phrasing comes second; ornamentation ranks a distant third. I've heard flute players that blew me away who never used anything beyond the occasional roll. It should go without saying, but if your rhythm is shaky, you really shouldn't be trying to tackle double-cut rolls. Build the wall first, then paint it.
Don't try to learn everything at once. Pick one or two techniques and focus on them, then move on to the next. Set reasonable goals. Learning to play this music will take the rest of your life, no matter how big a chunk you try to bite off right now. So relax and take your time.
It can't be overstated that the way to learn how to use ornaments is to listen to lots of good flute players. Get into the habit of recognizing what ornaments a player is using and noticing how (s)he is using them. If you understand how Matt Molloy uses cuts and taps, or can compare his use of cranns with Catherine McEvoy's, then you're a lot more likely to use your technique in a traditionally informed manner; moreover, you're equipped to make your own stylistic decisions.
Use ornaments on purpose. Don't just wiggle your fingers around and hope a roll will fall out of the flute. You might as well hit a computer keyboard randomly and hope you'll type "chrysanthemum."
Be able to visualize what you're trying to accomplish with every ornament you play. Why are you cranning that note? What is it supposed to sound like?
Used correctly, your ornamentation shouldn't draw attention to itself. It's a tool that aids in the expression of melody and rhythm. Making your listener say "ah! a crann!" is not your goal.
"Let us try to grasp the secrets of technique so well that people will be taken in and swear by all that is holy that we have no technique. Let our work be so savant that it seems naive and does not reek of our cleverness." --Vincent Van Gogh, from a letter to Anthon van Reppard, March 1884.