One thing you can do is offer free escrow services. There is a user called Monbux with a ton of trusted feedback from doing this. You do need to be trustworthy to get started, but you can start small. So for example, start in the currency exchange section whenever you need to trade bitcoin for Paypal or something. Start with small amounts and ask for positive feedback for successful trades. Once you start having trusted feedback you can offer free escrow services where you hold a small amount of bitcoin for people and settle disputes if something goes wrong.
With all due respect, starting out offering escrow services is a sure way to be stamped as not being trustworthy.
I have seen many users getting a very bad start by doing this.
The best way to "earn" trust is to start with being a good community member, make good posts and contribute the community.
The actual "trust" is in most cases given based on a some type of trade or business relation.
In order to trade, then will you need a product, either digital, physical or a service.
In any cases will you have to use a recognized escrow for the trade, most people will not trust a person with no record.
After some time will you start to have a trade record and together with your community contribution can the person that potentially will trust you have an idea what type of person/trader you are and use this as parameter in the trust evaluation of you.