If you are using the Default Header and you need to hide the post info you have in some single blog, paste this code in the Theme Options > CSS:

.post-info{
display: none;
}

Use this code to hide the date, categories and authors selectively:

.post-info .date-info{ 
display: none; 
} 

.post-info .category-info{ 
display: none; 
} 

.post-info .author-info{ 
display: none; 
}

Use this code to hide social share options selectively:

.share-button.share-inline .social.top li.social-facebook,
.share-button.share-inline .social.top li.social-twitter,
.share-button.share-inline .social.top li.social-gplus,
.share-button.share-inline .social.top li.social-pinterest,
.share-button.share-inline .social.top li.social-linkedin,
.share-button.share-inline .social.top li.social-xing,
.share-button.share-inline .social.top li.social-paper-plane{
display: none !important;
}