This page describes the responsibilities of the 5 player. It is directed at BB Men's and Women's teams (since the stategies change at different levels)
If all goes well, this should describe what you should be doing. Different teams have different strategies. But when it comes to defence, if there's a whole: fill it!
============ [ p4 p3 p2 ] [ ] [ p5 p6 p1 ]
This is an exciting position to play (like most!). You have the opportunity for a lot of action. However, this position is often poorly played. Remember that you should understand this position even if you don't play it, the reason is that there will usually be at least one rotation where you have to play this spot.
Expect the ball! Even though at first it might seem like the ball doesn't get blocked in your direction often, tell yourself that you know the ball is coming to you, and you have to dig it up. Tell yourself there is a huge block up there and there is no way the hitter could get around them. Anything to get you ready for the ball coming back.
==================== [ p3 ] [ p4 p2 ] [--------p1--------] [ ] [ ] [ r p5 p6 ] [ ]
Note that you get to this position after the hitter. If you get there early, it is quite likely that the hitter will run over you. Also look at the blockers hands, this will help you spot the ball as it comes back.
==================== [p4 p3 ] [ ] [p5--p1------------] [ p2 ] [ ] [ p6 ] [ ]
It is also helpful to be diagonal, since p4 does have much time to move back. It is important for you to move even if p4 doesn't. If they don't, yell at them a few times. Tell them that just because they didn't get set, doesn't mean they don't have something to do! If you move, they will hopefully see the huge space that they have to fill.
==================== [ p3 p2] [ ] [------------p1--p6] [ p4 ] [ ] [ p5 ] [ ]
It's best not to hit towards the middle, since many teams have tall lanky middles that would love nothing better than to stuff your back-row hit.
==================== [ p3 ] [p4 ] [--p5--p1----------] [ p2 ] [ ] [ p6 ] [ ]
I'm not so sure what would be a good defense here. One would think in the scheme I have below that the setter would come back to play doubles!
==================== [ p3 ] [ p4 p2 ] [--------p6--------] [ p1 ] [ ] [ p5 ] [ ]
6-2 - Who knows what happens to get to this situation. Probably the ball went to the front and set back or shanked to the back right (you) and you set the setter!
Maybe something like this.
==================== [ p3 ] [ p2] [--------p4---p1---] [ ] [ p5 ] [ p6 ] [ ]5-1 - symmetric to when p5 hits. here I have indicated p5 lower than the symetric pattern. We notice that p4 has to move all the way in to cover, given that they will coming from along the 3m line, they will cover the front pretty well. But if they are really quick and get in nice at tight for coverage, move more forward (to make sure you can get the one that blocks sideways).
==================== [ p3 ] [ p2] [---------p4---p1--] [ ] [ p5 ] [ p6 ] [ ]