There are many things that I don’t like about Microsoft, but gameplay for Halo is a sort of bittersweet. On the one hand, it’s an exceptionally fun game to play, but the opposite half of the case is that the plot is incomprehensible.
Note that the plot is there, though. It’s just that for some odd reason, be it writing talent or (more synically) an attempt to get people to buy the books and other memorabilia, the events in the plot are very difficult to pinpoint.
I can’t exactly fault them for this, my greatest weakness as a writing is having trouble expressing important points, after all. However, that just means that there is plenty of room to learn what NOT to do.
The rule for avoiding unclear plots is more of a guide-line again; dedicate at least a paragraph to explaining each concept and plot-point to your reader. This sounds simple, but it easier said than done if vagueness is one of your writing vices, but it at least gets you to start thinking in the right direction for making yourself be understood. Conciously trying to explain every facet of what’s going on helps keep you from assuming that everyone else knows what you know. However, know that 50% of the work is going to be done in the editing phase.
When editing, always keep the five ‘w’s plus ‘how’ in mind. Why is the sword talking? Where is the pedestal again? Is this a flash-back, or happening right now? etc. Be sure to replace every generic word with a specific one wherever possible. Bring in proof readers, too, and ask them to put a high emphasis on the clarity. Practise these, and you’ll be on the way to crystal clear scenes and plots.