When you are looking for a pug, you should always have some general guidelines to provide your pug with so that things are clear.
Here are the rules I would expect a pug to follow.
1. Let us know how long you can stay so that there are no surprises in the middle of the raid that we need to replace you
2. Don't come doing white damage and expect to take loot
3. Patterns/recipes etc go our guild first if someone needs it
4. We may ask you not to roll on a specific item that a guildie has been waiting for
5. You may roll on any other items aside from the above mentioned
6. Don't get greedy ....roll only on items that are an upgrade
7. Don't roll on stuff, just to DE it
8. BOE stuff, unless it is an upgrade for you, will go to our gbank
9. Don't create drama with nasty talk and complaints...we've been doing this raiding thing a while and have succeeded many times without you
10. If things go well we would love to invite you back as a regular pug with our guild
Most of us hate pugging ourselves and hate having to invite pugs to our raids. I definately have expectations of pugs who come into our raids. I also expect when our guildies are pugging themselves out to be just as courteous and represent the guild well.
Be fair and clear about the rules up front with your pugs so that there are no misunderstandings. They are part of your team for that period of time and things will go smoothly provided they know what is expected of them.