I have to say, my jackpot playing strategy is much simpler than everyone else here.
I guess I play as I would the lottery... when the stakes are high. Mostly because it's akin to playing the lottery - you know in your heart it probably won't be you, but you can help but buy one ticket... just to hope? Dream?
Look at Mega Moolah (microgaming) right now, it's at over 6.4 million. Heard that bigger than it's ever gotten. You bet I've spun a couple of spins when I'm running at the end of a good slot session, and just want to run my cash to the ground.
But to answer your question
[*] How do you normally select the (progressive) slot to play? - Generally I keep an eye out for the big ones, and play when they get to that point where they usually burst. Plus I make sure I play on the jackpot slots that are fun too. I quite like the IGT Megajackpot Cleopatra at the moment. I know it's probably not as good returns as the actual Cleopatra, but I have fun and good results playing on the jackpot. Mega Fortune is also a favourite as it low variance, so keeps you playing for a while.
[*] Do you care much about the RTP of the slots? - Sure. I always check the RTP and make sure it's at least over the 94%. But like the guys have all commented on, you have to accept that the RTP will be slightly lower than on a non-progressive machine.
[*] How do you judge whether a progressive jackpot is "hot" and likely to soon be paid? I don't. Not really. Sure I start paying attention with Mega Moolah and Hall of Gods are over 4 million and Mega Fortune is over 6 million... but i've played when they've been much lower too. So can hardly say I only play when they are.
Not a fan of Playtech jackpot slots, I have to say. Just cause I haven't had much fun (luck?) playing them to be honest and they usually require a really high max bet to win anything.
That said, I'm not what you'd call a 'high roller' gambler, and many of these progressive tend to favour larger bets. So I just take my chances with the machines that sometimes like to pay out to casual gamblers like me.
I think that as long as you enter jackpot slots the same way you do slots in general, it can add a little thrill.
That said, I do usually leave the jackpot slots for the end of my play session, rather than beginning! Because... you know... I still want to
win something worthwhile before going for the jackpot slots that generally pay out less.