A good guild in my opinion is a friendly and active one. Whether it be helping each other out or even working together to help others out (Who aren't necesarilly in a guild), I seem to be drawn to those types of guilds ^-^
I do prefer people who don't curse and thankfully not alot of people in my guild actually do that, we usually use 'Dang' or 'Fudge' etc. Just a preference, I know some people don't mind cursing.

A good guild master would be also friendly and active, someone who will help you when you need it (If they have time ofcourse).
Someone who is a good example who people can aspire to be like :3

I don't see skill to necesarilly be what determines a guild as 'Good' where others would but skill, I guess, does have to play a part. I mean I wouldn't be where I am if I hadn't been taught by the more skilled players in my guild, and now, I get to teach others too ^-^ Although I am far from the best.
It's all about community, activeness and friendliness with me. Whut can I say, I love a good chat xP

(There are alot of 'good' guilds, just some are more well known than others).

~The Mighty Cheese Knight; WeeGee