There is a lot of good advice in this thread. I have been lurking and thought I would add my two cents...
I was never d'fd but I have been faking being a witness for years. Since I was baptized really.
But I don't want to leave regardless of my beliefs because my family is more important than myself. (no ill will to those that feel differently it is just the way I am)... So faking being a good dub isn't as bad as most people think. I even smoke and have not had trouble. (yet)
1. Take something to do during the meetings. I have found that suduko cut out of newspapers slipped in my bible make me look nice and studious. I also write short stories.
2. You have to go in service. Most of the congregations have one Saturday where the whole congregation meets together instead of just at the book study. This is the best time to go. You get the maximum exposure for the least amount of effort. I claim to be very shy and ask other people to talk at the door for me. Usually you are working with different people and can spread this around a bit. Also I am very famous for being a "breakfast" kind of service guy. On the rare occasion I do have to talk at a door I read a scripture. Then I lie on my service report and always put the average for the congregation from two months back.
3. Sometimes its a good idea to do a nice heartfelt comment. This means you read the sentence in the paragraph and add a "this thought really meant allot to me" at the beginning or the end of it. Sometimes it helps to para-phrase
4. Being social.. I like talking to people. I keep a few "spiritual thoughts" tucked away in my head for when people want to talk about it. I was tipped off to this a few years ago when I overheard someone saying something to the effect of "IMBA never talks about spiritual things". So now when the conversation goes that way I have something to say. Even if it is fluff, they expect you to pretend to be a bible scholar remember. Talking about “the strength of the demons” is a good one because they love to talk about demons for some reason.
5. Most importantly keep your thoughts/complaints/reactions to yourself. Until you meet someone that you can trust with them. And be careful half the people you think you can trust you can't. More than half really. But there are those out there that will listen to theories and thoughts if presented the right way. But it has to be approached carefully. There are a few hot button topics that if you come barreling in with them they are going to KNOW that you have been talking with the "evil apostates". IE - 607, United Nations, COC, etc.. Try to be more subtle. Talk about things that make it look like your just being a good student. And end your sentences with something vague like, "I can't want until we get clarification on this," or "perhaps we will find the answers when the new scrolls are opened."
Coming back in from being D'fd has got to be much harder. There is that whole waiting period and sucking up. But I like to think that I am floating instead of fading. I am basically agnostic so I don't really care what people believe. And when you're entire family (many generations) and social circle is made up of this it is hard to break away. Mostly I just to be with the people I love.
Good Luck!