I can only speak from experience: I had an eye examination, taking my eye dimensions at the same time. Once they had my measurements and prescription strength, my optician recommended a lens for me, and gave me free samples to try. I put in a pair whilst there, and using something that resembled a litnus paper, he put some dye (luminous yellow) into my eye. Then he examined my eyes whilst shining a light into my face. (I guess the dye appears luminous and shows whether it's a good fit or not). I then kept them in for a few hours (I've worn them for over 15 years so I used to them) and I reported back. As this is your first time, you might only keep them in for 30 mins or so. Your optician will advise you.
Although there is an element of trying it to see how it fits, it's not really like trying glasses - so it's unlikely you'll need to try more a couple or so.
My husband recently changed over to lens and he took to them straight away, and only need two visits - one for the first fitting, and second to check the fit and confirm that all was fine.
There's nowt to it!