What properties should I set to nil in viewDidUnload?-Collection of common programming errors

I don’t know if I’m using viewDidUnload properly. Should I release all stuff I declare in my .h file?

Here is how I’m doing it now:

@property (strong, nonatomic) Readability *wrapper;
@property (strong, nonatomic) ArticleModel *article;
@property (strong, nonatomic) Woho *wohoItem;
@property (strong, nonatomic) FeedItem *item;
@property (unsafe_unretained, nonatomic) IBOutlet UIScrollView *scrollView;
@property (strong, nonatomic) NSMutableArray *picturesArray;
@property (unsafe_unretained, nonatomic) IBOutlet UILabel *headTitleLabel;

and in viewDidUnload:

- (void)viewDidUnload
{
    [self setHeadTitleLabel:nil];
    [self setScrollView:nil];
    self.picturesArray = nil;
    self.item = nil;
    self.article = nil;
    self.wohoItem = nil;
    self.wrapper = nil;
}

Is this the right thing to do?

Probably not, because my app crash on every memory warning.

Thanks!