Every meeting I went to had at least one non religious person there - me.
How will you 'act' is the right terminology to use, because you will need to hide your disbelief. What you see and hear will be a mixture of the surreal and fantastical.
Get your reasons ready for being there. 'Research' will probably arouse some suspicion, even if they are not obvious about it. And I wouldn't mention any higher education you have.
Watch Tower day will be best for just 'blending in'. Midweek will very much feel like you're in a classroom and that more eyes are on you.
Be prepared to sing, or pretend to. Someone will share their tablet with the lyrics with you. The tune is immaterial and usually indiscernible.
Turn your phone down or off, unless you want a ready made excuse to dart out the door.
Get your reasons ready not to have a bible study with someone, unless you want to of course.
Clear a big space at home - near your recycling bin is best - for the literature you will be given.
The urge to run will come. if it doesn't. return here for regular deprogramming.
It's possible to fake it for a long time. I could still be there if I wanted to. They want new recruits. You won't get thrown out, even if they suspect you're not fully in. It's just a matter of how long you can keep up your story and motivation.
Despite the initially-interesting strangeness of the 'JW life' to an outsider, it is, at its heart, very mundane and monotonous.