I'm happy to see that the 3 choices that made the most sense to me, so far seem to be the majority's choice as well!
In case it changes over the next few days, i'll post them and add my line of thought:
Choice of software:
For me the most important, if they don't have at least one or two of my preferred providers, i can save myself a lot of time checking to see if the Casino actually is worthwhile
Accredited or recommended by CM or other respectable portal:
Not perse a necessity, but definitely a heavy weighing factor, as when it
is a Casino that is recommended here or on my other forums, i also feel a lot safer, and can skip some of the checks i would need to do when it wouldn't be..After all, i, like most fellow punters, do like to 'plug and play' as opposed to the 'read T&C's for an hour, spitting through all the sections in the site, and scour the internet for possible bad news RE; this particular Casino'
Loyalty scheme - ongoing bonuses:
One of the most important things to me is getting rewarded for my loyalty: i do like the occasional Match up, and i expect them aside from any welcome package. Even better when there are comp-points, a good (and reasonably achievable) VIP-program, or personal attention from support or management in the form of comps for loyalty, goodwill, or streaks of bad luck.
Of course point three is not always clear from the get go, but sometimes when looking for a 'new' Casino, you end up at an already established one, and you can read and learn about this from feedback from fellow punters on forums such as these.