Be Honest - Be honest about what was done. It's unusual to find someone who hasn't performed few questionable marketing once. A great client explains what they've done so their provider can figure out how to fix and deal with it faster.
Don't Blame Links When Something Goes Wrong - Don't blame links if your SEO service provider has built one for you and you end-up messing up their robots.txt file.
Sudden URL Changes - Don't change URLs without informing your SEO service provider on this matter. If you've given some targets to work with and they suddenly 404ed, that's embarrassing. Webmasters get cranky when you have to go back requesting for a change.
Share Access to Webmaster Tools, Social Media Networking sites and Analytics - If your SEO provider doesn't know what's happening, it's difficult to complete a good job. It's significantly easier if they can start immediately instead of waiting for you to come back from your week long getaway.
Answer Questions - Answering questions doesn’t mean being nosey. SEO’s asks because it affects their work.
Listen to Risk Advices - If your provider says that your linking structure is risky, it probably is. A good company won’t risk its reputation just for money.
Don't Share Someone Else's Confidential Information - It’s just plain etiquette. Clearly, you don’t want your trade secret being leaked.
Say what you really want - Don't start out asking for services and then make your provider run all around and eventually admit that you want something totally different. Get straight to the point to avoid spending valuable time.
Ask Why a Service Costs and how it works - It's best to explain pricing now than receive complaints about it later.
Be reasonable regarding Client Examples - Don't panic when your service provider can't provide examples you prefer when you're deciding if they're the ideal fit. Iron-clad nondisclosure agreements exist for a reason.
If your provider is unable to present you client examples but are willing to work for you under the condition of a refund if you're not satisfied, either accept that offer or move on instead of sending rude emails about lack of professionalism.
Master Link Builders Knows More Than Just Building Links - If you're asked to promote your new content socially to gather attention, take that advice. Don't just think that because you can't connect social to links instantly, it implies that the advice is ineffective.
Don't Focus and compare What Your Competitors Are Doing - Don't constantly suggest what your competitor is doing that breaches Google's guidelines and ask your SEO's why they don't mirror it. That’s black hat and a no-no!
To begin with, your site isn't the same as their site. What's more, if you build a copied profile, you’re violating the rules and regulations of Google, and that's not a good thing.
Do not do unto others what you don't want them do unto you.
Don't always ask service for free - I doubt you'd find a decent SEO who gives way too much freebies. If you did find one, be suspicious!
If you're paying them for their expertise, then acknowledge that relationship. Understand that most SEO marketing companies really wish to accomplish an excellent job for you. The more they know, the better they can perform.