Stop post automatically appearing on Home grid?

@jake: hi i can suggest a solution for you, you can try this:

At first, you need to add a new metabox to Post page to make option that can exclude the post from home page like this :

function dw_fixel_exclude_post_in_home() {
    add_meta_box( 'dw_fixel_exclude_post_in_home', 'Exclude ?', 'dw_fixel_exclude_post_in_home_callback', 'post', 'normal','low');
}
add_action( 'admin_init', 'dw_fixel_exclude_post_in_home' );

function dw_fixel_exclude_post_in_home_callback() {
?>
    <table>
        <tr>
            <td> Exclude from home page? </td>
            <td>
                <?php 
                    $dwpb_enable = get_post_meta( get_the_ID(), '_dw_fixel_exclude_enable', true );
                        $dw_fixel_exclude_from_hompage = '';
                        if ( $dwpb_enable == 'yes' ) {
                            $dw_fixel_exclude_from_hompage = 'checked';
                        }
                ?>
                <label style="margin-right: 50px;"><input type="radio" name="dwpb_enable" value="no" checked><?php _e('No','dw-fixel') ?></label>
                <label style="margin-right: 50px;"><input type="radio" name="dwpb_enable" value="yes" <?php echo $dw_fixel_exclude_from_hompage; ?> ><?php _e('Yes','dw-fix') ?></label>
            </td>
        </tr>
    </table>
<?php
}

function dw_fixel_include_post_in_home_save() {
    if( ! empty( $_POST['dwpb_enable'] ) ) {
        update_post_meta( get_the_ID(), '_dw_fixel_exclude_enable', $_POST['dwpb_enable'] );
    }
}
add_action( 'save_post', 'dw_fixel_include_post_in_home_save' );

After that , you can go to file index.php,
from line 9–>21 change the code like this :

<?php  while( have_posts() ) : the_post(); ?>
            <?php 
            if ( 'yes' != get_post_meta( get_the_ID(), '_dw_fixel_exclude_enable', true ) ) {
                    $block_class = 'block';
                    if( dw_is_featured_post() ) { 
                        $block_class .= ' w2';
                    } 
                    if ( $first && ! dw_is_featured_post() ) {
                        $first = false;
                        $block_class .= ' grid-sizer';
                    }
                ?>
                <?php get_template_part( 'content', get_post_format() ); ?>
            } 
        <?php endwhile; ?>

Hope it help.

@Dominic – thanks, I added the functions to functions.php and can see the metabox now. However, when I add a new test Post, select "Exclude from home page", then publish it seems to have no effect, i.e. the Post still appears on the home page.

As per instructions above, the theme’s index.php file has been modified as below. (I assume the functions.php file is correctly amended since I can see the metabox – I simply pasted the above functions to the bottom of the functions.php file):

<?php 
global $paged, $block_class, $paged;

get_header(); 
?>  
<?php if( have_posts() ) : ?>
    <div id="main" role="main" class="masonry" >
        <?php $first = true; ?>

        <?php  while( have_posts() ) : the_post(); ?>
            <?php 
            if ( 'yes' != get_post_meta( get_the_ID(), '_dw_fixel_exclude_enable', true ) ) {
                    $block_class = 'block';
                    if( dw_is_featured_post() ) { 
                        $block_class .= ' w2';
                    } 
                    if ( $first && ! dw_is_featured_post() ) {
                        $first = false;
                        $block_class .= ' grid-sizer';
                    }
                ?>
                <?php get_template_part( 'content', get_post_format() ); ?>
            } 
        <?php endwhile; ?>

        <?php dw_paging_nav(); ?>
    </div>
    <?php dw_show_more_button(); ?>
<?php else: ?>
    <?php get_template_part( 'content', 'none' ) ?>
<?php endif; ?>
<?php get_footer(); ?>

Any ideas? Thanks!