First, you need to make some trades to show that you are a man who knows the business. It also proves how much money you have. A stable escrow is one with a lot more in his wallet than the amount he trades. I have met many who honestly refuses an escrow request because the held amount is more than their current possessions.
Second, you need to be an old reputed member here so that people trust you and know you from long. New comers are always risky to invest our trust.
Third, you need a good and attractive resume in the form of a webpage, post or in a blog. You need to first offer free escrow servicing and start with small trade amounts.
Finally, you should know yourself and be a calm person.
How do you show other people that you have done a lot of trade?