Don't join a guild until you're at least halfway to max level. The reputation of a guild during its members leveling up will make or break it, and you don't want your name/reputation associated with the 2 or 3 socially toxic guilds on the server, even if they are the largest.
Stop and sniff the roses - almost all of the fun in a good MMO is getting to maximum level not actually being at maximum level.
Be careful of the bees. If you get stung. your nose swells up, you cannot breathe and you die, not only is there a severe death penalty but you will be swarmed by people laughing at you. Oh the embarassment.
Group up with other players right away. Begin to learn the best ways to compliment each other in combat. Hunting is safer in groups and leads to better rewards. Then show them how to setup your basic group Macros. Explain the basics of group etiqette as it applies to Pantheon.
Reach out, tread carefully, team up, turn off your stop watch or take off your rush-mash-button cap.
And read what the game is giving you as information (npc's, books, documents etc)