Wait are we talking about the anti-ending crowd then or the pro-ending crowd now? 
It shouldn't matter. Nasty language is disrespectful whether I agree or disagree with your opinion on a game. I'm also thinking of that whole mess with Hepler too; that's part of the fallout from DA2 of course, but it was a sign of what was to come with ME3.
On topic:
1. Going into detail would spoil the game, so all I'll say is play the game with the save you've got the way you want, then if anyone does die, read up on how to change that.
2. I'd recommend making a round of the ship after every mission, at the very least after every mission marked Priority; not only can you miss out on some important conversations, but you can miss out on bonus powers too. Also, crew members move around the ship; check the map before you go. Also, if there's more than one character together, don't start talking to them straight away; they may be having a conversation you can listen in on, and sometimes take part in.
3. There's a lot to Citadel. I'd recommend playing the story mission half-way through the game, since it unlocks a lot of stuff that you can use throughout the rest of the game, like a battle arena and an ME1-style weapon with cooldown instead of ammo. After the story mission, a party is mentioned. You can hold the party at any point before the final mission (you'll be warned when you're passing the point of no return), and I'd recommend holding off as long as possible.
4. Going into detail would be a spoiler. All I'll say is that some people hate the endings and some people like them. I like them.
6. Don't worry, it's only the trilogy that's ended. The series goes on, for now.