When in a guild or thinking about joining a guild there are things I think you should do/know!

1) Greeting

When someone joins your guild, or you join a party, try welcoming them and saying hi. It's always nice to here people saying hi to you.

2) Politeness/ Manners

Being polite is always considered a good thing. A little please and thank you goes along way.
Try not to invite people to a group, even for a quest, without speaking to them first I.E asking to group up.

3) Giving and Taking

If a player does you a favour, try offering your services in return. I.E If a guildie makes something for you free of charge, offer to do something in return. It can stop them from feeling used
This is also part of Politeness/ Manners.

4) Partying Up

If you see a player struggling on a quest I.E the mob/boss is too high level or just too hard, trying /w that player to see if they want help.
When on a quest and you see a lot of players waiting to do the same quest as you I.E killing a special mob, make a suggestion to them about partying up and doing it as a group. That way you won't have to fight about who kills it etc.

5) Prejudice/ Stereotyping should be avoided.

If you are talking in guild chat or trade etc, try to avoid harmful remarks. I.E GAY!! Yes that is just a way of relieving stress but some people make take it the wrong way. I for one have done it myself, it is not nice to say stuff like that.
Even a small Stereotyping like calling people who are Blonde dumb, can be a insult. Rather then starting a fight in chat, try thinking about what your writing first or check what you've written. Consider those who may take in offensively.

This is just some of the ways you can be a nice/good player that people will enjoy!

Hope you enjoyed reading this.

-Focal