How I do my WordPRess site specific configuration fields

custom.php

<?php

/* setup custom general settings */
function ts_theme_settings () {

  register_setting( 'general', 'homepage_slider_wide' );
  add_settings_field(
    'homepage_slider_wide',
    'Homepage Slider (Wide)',
    'homepage_slider_wide_callback',
    'general'
  );

  register_setting( 'general', 'homepage_slider_narrow' );
  add_settings_field(
    'homepage_slider_narrow',
    'Homepage Slider (Narrow)',
    'homepage_slider_narrow_callback',
    'general'
  );

  register_setting( 'general', 'footer_disclaimer' );
  add_settings_field(
    'footer_disclaimer',
    'Footer Disclaimer',
    'footer_disclaimer_callback',
    'general'
  );

  register_setting( 'general', 'site_phone' );
  add_settings_field(
    'site_phone',
    'Contact Phone',
    'site_phone_callback',
    'general'
  );
  register_setting( 'general', 'social_fb' );
  add_settings_field(
    'social_fb',
    'Facebook Link',
    'social_fb_callback',
    'general'
  );
  register_setting( 'general', 'social_yt' );
  add_settings_field(
    'social_yt',
    'Youtube Link',
    'social_yt_callback',
    'general'
  );
  register_setting( 'general', 'social_tw' );
  add_settings_field(
    'social_tw',
    'Twitter Link',
    'social_tw_callback',
    'general'
  );
  register_setting( 'general', 'social_pn' );
  add_settings_field(
    'social_pn',
    'Pintrest Link',
    'social_pn_callback',
    'general'
  );
  register_setting( 'general', 'ga_analytics' );
  add_settings_field(
    'ga_analytics',
    'Google Analytics Code',
    'ga_analytics_callback',
    'general'
  );
}
add_action( 'admin_init', 'ts_theme_settings' );

function homepage_slider_wide_callback ($args) {
  echo '<input class="regular-text ltr" type="text" id="homepage_slider_wide" name="homepage_slider_wide" value="' .  htmlspecialchars(get_option('homepage_slider_wide'), ENT_QUOTES, 'utf-8')  . '"/>';
  echo "<br>NOTE:  This is the whole short code for the full-width home page gallery, for example:  [nivoslider id=\"1315\"]or [nivoslider slug=\"home_wide-dev\"]";
}

function homepage_slider_narrow_callback ($args) {
  echo '<input class="regular-text ltr" type="text" id="homepage_slider_narrow" name="homepage_slider_narrow" value="' . htmlspecialchars(get_option('homepage_slider_narrow'), ENT_QUOTES, 'utf-8')  . '"/>';
  echo "<br>NOTE:  This is the whole short code for the tablet/mobile home page gallery, for example:  [nivoslider id=\"1316\"]or [nivoslider slug=\"home_narrow-dev\"]";
}

function footer_disclaimer_callback ($args) {
  echo '<input class="regular-text ltr" type="text" id="footer_disclaimer" name="footer_disclaimer" value="' . get_option('footer_disclaimer') . '"/>';
  //echo "<br>NOTE:  Use the whole address, including http://-- like https://www.facebook.com/john.r.reeve";
}

function site_phone_callback ($args) {
  echo '<input class="regular-text ltr" type="text" id="site_phone" name="site_phone" value="' . get_option('site_phone') . '"/>';
  echo "<br>NOTE:  Whole phone number - 800-555-5555";
}

function social_fb_callback ($args) {
  echo '<input class="regular-text ltr" type="text" id="social_fb" name="social_fb" value="' . get_option('social_fb') . '"/>';
  echo "<br>NOTE:  Use the whole address, including http://-- like https://www.facebook.com/john.r.reeve";
}

function social_yt_callback ($args) {
  echo '<input class="regular-text ltr" type="text" id="social_yt" name="social_yt" value="' . get_option('social_yt') . '"/>';
  echo "<br>NOTE:  Use the whole address for external links including http://-- like http://www.youtube.com/user/ERB";
}

function social_tw_callback ($args) {
  echo '<input class="regular-text ltr" type="text" id="social_tw" name="social_tw" value="' . get_option('social_tw') . '"/>';
  echo "<br>NOTE:  Use the whole address, including http://-- like https://www.facebook.com/john.r.reeve";
}

function social_pn_callback ($args) {
  echo '<input class="regular-text ltr" type="text" id="social_pn" name="social_pn" value="' . get_option('social_pn') . '"/>';
  echo "<br>NOTE:  Use the whole address, including http://-- like http://www.pinterest.com/gibsonguitar/";
}

function ga_analytics_callback ($args) {
  echo '<input class="regular-text ltr" type="text" id="ga_analytics" name="ga_analytics" value="' . get_option('ga_analytics') . '"/>';
  echo "<br>NOTE:  This should take the form UA-XXXXX-Y";
}