Buyers

Detailed Project Description
Your project description should be as detailed as possible. It's better to have too much information than too little. Some people choose to summarize the project in the description field, and attach a file with more detailed info (for interested bidders). Which is a good idea.

Additional Features
If you have additional features you would like in your description, which you did not mention in the project description, please tell the seller BEFORE they begin work.

Payment Method
Before the work begins, you should discuss with the seller how you will send payment. Begmetobuyit suggests puting money in an escrow account.

Sellers

Know The Project
You should know how you will sell the good/service before you place your bid. If you need more details, post on the message board for that project, request more information from the buyer/project manager. If you don't, at least make sure you are clear about the project before you begin working on it.

Updates
You might consider updating the buyer on your progress throughout your work, especially if it's a difficult and complicated job/project. This will assure that there is no confusion over how the good/service is suppose to be when you completed the project as agreed.