The main way to help users to trust you is be worthy of your users' trust, and make it apparent to your users why you are worthy of their trust. There are various ways to establish that you are worthy of trust. The details are likely to be specific to your particular site, but here are some examples from other domains.
One way is through branding: if your brand is familiar (e.g., the user has had positive interactions with you before, or they have heard positively about you from friends or family), they will be more likely to trust you.
Another suggestion is to ensure that everything you do is in the customer's interest -- and make this apparent to the customer. Don't be "sleazy".
For example, don't ask for the user's address or phone number just because you want it or because it would let you send the user marketing. Wait until a point arises when the user will get some tangible benefit from providing this information, and then allow them to provide it. For instance, it is one thing to ask for your customer's shipping address and phone number when they want to order something and have it mailed to them; it is another to require them to provide this information just to create an account with you. If you must ask at account creation time, make it optional and allow them to provide it later when it is needed.
Another way is to provide user-friendly policies. Think of mail-order companies, which promise that if you don't like what you ordered, you can return it for a refund, with no questions asked. Think of Zappos, which not only offers no-questions-asked returns, but will even pay return shipping. That can increase confidence among customers and give them peace of mind that if they don't like what they ordered, they can get their money back.