There are several important aspects to making a useable plotline. First, you must have a beginning and you must have an end.

What? You mean I can't just start with a beginning and see where the characters go?

No, No, No. Your characters, while they are 'living' people who must interact with a 'real' world, must have events and things happen to them, that help determine who they will become and what they must do.

Thus, enter destiny characters. These are the characters that MUST do something, and MUST be somewhere in order for the rest to happen. Destiny characters are found in many stories.

But, what does destiny characters have to do with a plotline?

Simple, for the sake of plotting, you will have destiny characters, so they are destined to reach the end you want.

Trust me, it is much easier to follow through on a plotline when you know where you need to go.

That is the most simplistic plot that you can have. The beginning and your end. The rest can fall inbetween, will or nil it be expected. You now have the basics of a plotline for use.

Now, when I plot, I take this a step further. I, like many people, find that my characters need a little degree of freedom. However, they also need a little degree of things happening in their direct world. These are the challenges that they must face and react to.

These are your plot points. You need these too, if you want to try to follow a plotline. So, take your beginning, your plot points, and your end. Now, you have everything that you need to write your novel. Below, you will find a plotline that I have thrown together on the fly as an example.

Main Plot: Boy and Girl must save the world. (Complex, huh?)
Beginning: Boy lives in small town, middle of nowhere. His family is attacked by a raiding party of rabid monkies. (Hey, I never said I couldn't have FUN with this..)
Plot Point 1: Boy flees the rabid monkies and is rescued by Monkey-Hunters.
Plot Point 2: Boy joins Monkey-Hunters to get revenge.
Plot Point 3: On a Monkey Hunt, Boy Rescues Girl.
Plot Point 4: They return to base city to find it destroyed.
Plot Point 5: Boy seeks vengence for the destruction of city.
Plot Point 6: Girl Rescues Boy after he tries to take on someone too big for him.
Plot Point 7: They recruit a bunch of men to try to save the next city from destruction.
End: Boy and Girl defeat the bad dude who destroyed said city.

As you can tell, there is a lot of flexibility here. You have several choices now. You can take this, and see where your characters go, making certain to hit at these points, OR you can expand it further. Below, you will find another expansion of this really weird plot. For sake of sanity, I am expanding only three of the plot points.

Plot Point 1: Boy flees the rabid monkies and is rescued by Monkey-Hunters.
-- After he is protected by Monkey-Hunters, they find his family
-- Returns to Cottage to get his belongings
-- Leaves with Monkey-Hunters, returns to their base

Plot Point 2: Boy joins Monkey-Hunters to get revenge.
-- Starts off as a trainee
-- Goes on easy mission, succeeds
-- Officially inducted into the Monkey-Hunter Society

Plot Point 3: On a Monkey Hunt, Boy Rescues Girl.
-- This is his fourth or fifth mission (time passes)
-- Boy disobeys orders by chasing after a stray Monkey to find girl
-- Becomes a bit of a hero for saving girl
-- He is still disciplined for actions though

This is how I tend to plot, although I list mine by titles of the required scene. (IE, just remove the Plot Point: # part, and thats how I list mine.) This gives me the flexibility I need to write without feeling massively constrained, but it lets me guide the story enough to catch plot holes before I WRITE the plot holes. It also helps me gauge the tension and pacing so I know whether or not I need to add a more 'active' scene into it. Your plot, you will notice, WILL fluctuate slightly as you write. However, you will want to make certain the PRIMARY plot points stay the same after you have added them. (Go ahead and Add the MONKEY MASTER! (bwahahah) into your plots afterwards, as long as you account for the actions of your protagonist. I added my antagonist after a third of my book was written with no problems, because I made certain I calculated his actions while plotting the actions of my poor Destiny Characters.

That is all I really do, beyond asking myself questions and answering them on my notes sheet and keeping track of names and places. I find this simplistic plot line is easy to follow and prevents deviations from the line I want the novel to take.

It takes practice, so be aware of that. However, once you have the hang of it, I find this version of plotting (if you're going to plot at all) works best for me.