You can opt in for the beta at the official site. When the beta launches on May 15, players who’ve gotten in will be able to play all the way from from level one to 30. WoW game director Ion Hazzikostas tells us that the beta will be “uncharacteristically small compared to our expansions,” in part to ensure that the focus is on the proper launch this August.

A lot has happened in World of Warcraft in the fifteen years since it originally launched, and over that time we’ve come to expect certain things, not just in WoW, but in games in general. As players explore Azeroth as it existed back in 2006 during the WoW Classic beta, they’re reporting bugs – but in many cases, these ‘bugs’ are really just features that are working as intended.
The priest was considered the best overall healer in vanilla WoW. Priests had the biggest selection of healing and defensive spells which could be used in various different situations. Due to this fact, Priests had an easy time finding groups and guilds. If you’ll embark on leveling priest, expect some random whispers from other players inviting you to join their group as a healer. Shadow Priests were also considered as one of the best duelists in the game boasting with serious damage and healing.

 ":"  -  Any time a step ends in a ":" instead of a "." means that the next step is part of the current step you are on.  This generally means the next step should be done while working on the current step.  This means every "start working on" or "continue working on" will end in a ":".  But this is used with other occasions as well, so keep this in mind.
Wait, /sit to trigger crits is p-server thing? I distinctly remember people saying that if you sit, you will be crit when I played 1.12 Vanilla. On top of that - there’s that pally that one shot Kazzak in early Vanilla because he stacked a shitload of reckoning when it didn’t have a limit - it’s not inconceivable that he did it without /sit to trigger crits, but it would take him so, SO long to do that without /sit.

The quickest way to level up is to travel through the game's zones, completing all the quests you encounter along the way. Completing quests grants you Experience points, which will slowly fill in your experience bar with blue or purple. When the bar fills, you reach the next level. Alternatively, you could choose to run Dungeons or Battlegrounds, which are not covered in this beginner's guide.