1. For a telephone link (once clicked, calls a number), begin with a normal "<a href=" link tag. For the href, specify "tel:" then type the phone number, making sure to include the country code. Close the tag with a ">"
2. Type the phone number, then the closing tag </a>. It's important to add the phone number in case the visitor's mobile phone doesn't support tel: links
3. Do the same, with "callto:" instead of "tel:" for a Skype link. While a tel: link will only work in a mobile browser, a callto: link will work on desktops with Skype installed
4. For a texting link, do the same, but with "sms:". This will, of course, only work in mobile browsers
5. Style the links to be a different color from normal text. This is optional, but will help mobile users know where to click.