Now, I forget the exact limits... I actually haven't watched the anime, and don't plan to. I'm about halfway through the manga, though. (I can't handle watching and reading the same series. Whichever I hear about first is the way I go, and if I hear about both, I go for the manga.) But if I recall correctly, there's some sort of time limit... I don't remember how the time limit works, though. So this is dependent on my being able to set certain parameters.
I know that you can write certain details in before the name, so what I would probably do is write, "confess your crime in writing, then die instantly," (or however you would word it,) but not put in a name.
I don't own a gun. I would like to, but A, I don't have money to spare on a gun right now, and B, I live in California. I have no desire to ever shoot a human being. In fact, I would probably prefer not to shoot even animals. But I am very much pro-guns, because I want to have the ability to protect my friends and family if the need arises. If it were just my life in danger, I don't know what I'd do. Maybe I'd just let the person kill me. But friends and family... Anyway, I don't have a gun. So if I were going to use the Death Note, I would use it in defense only. That is to say, it's easier to carry a notebook around without arousing suspicion than it is to carry a gun. And you can take a notebook into places like airplanes and such. So in an emergency, I would try to get the hostile's name, and then write it down.
There's also a special eraser, I believe, that can bring back people who were killed by the notebook. This is why I would want the crime confessed in writing- so that I could bring them back and have them put in jail instead. But let's say I couldn't get their name. I would also have written in the notebook something along the lines of, "if I die and my name is in this book, erase it with this particular eraser." Then, if I were in danger, I could write my own name in the book. I mean, I'm dead either way, but this way, there's a chance of my coming back.
Of course, this is all hypothetical. This is if the book existed and if it fell into my hands, then hypothetically, this is how I would use it if I were going to use it at all. Of course, if the book actually did exist, there would be a lot of theological questions regarding it that I would have to look into first.