For those who are interested.
Not sure if it's new or just something I have missed

You don't have to have another person that is in the guild online to get an invite... Here is the steps.
1. With the toon you want in the guild, hit the "J" key or click "Guild & Communities" tab.
2. Top left of that pop up window, click on "Guild Finder".
3. In the search box, top right, type in "pets" and hit search.
4. WarcraftPets should pop up in the results.
5. Click the "Request to Join" button at the bottom of the area where it talks about the guild.
6. Fill in the box is optional, but you have to choose a spec.. don't matter what one you choose, but have to, to make the "Apply" button turn red.
7. Click the "Apply" button.
8. Should now see "Pending" in the status of the guild info area.
9. Now wait till I get online, (which is daily), and I will approve your application.
10. Next time or later on

keep checking the "Guild & Communities" area. Once I have sent the invite, there should be a new button above Guild Finder that says .... "Invited to WarcraftPets" on the top right of that box that pops up.
11. Click "Invited to WarcraftPets"
12. Click "Accept"
13. Click "Accept" again.
14. Welcome to the Guild