What are the biggest challenges you face with regards to gaining potential customers trust?

What are the biggest challenges you face with regards to gaining potential customers trust?
Is word of mouth the only way to gain trust or would they accept user ratings and comments from an online community and/or directory?

Word of mouth is an excellent way to get through the customers' door, but the onus remain upon you (when you had a chance to meet customer face-to-face) to demonstrate that you can bring value to the customers' business by addressing their needs and/or concerns. Once given the opportunity to conduct any form of business dealing you MUST always win their trust and confidence, so that they believe that you (and your organisation) are dependable and trustworthy of their business.

Another approach is to attract the attention of your target customers through participation in professional conferences and trade exhibitions, writing technical articles about your products (features, quality, functionality, etc) and/or target advertising in professional magazines where you highlight key products / services differentiators.

If all possible, I would advise you to consider positioning your business in a niche market where custmers need your products, at whatever price, as there's (hopefully) hardly any competition.

Word of mouth is always best; testimonials and user ratings are great too.
You can also get a lot of customers from appearing in magazine or newspaper articles as that seems to suggest credibility.
If you offered a 100% money-back guarantee for your product or service that could help too.

I find these are the best ways to gain customers trust:

Be transparent in your dealings with them.
Treat them like a relationship and not a sale.
Be the best resource to them (whether your product/service or another)

Giving a straight answer to such a general Question is not possible.
We need to analyse the following
1. Level of Existence of the Firm in the Market
2. Its Market Share
3. Technical Level of the Product
4. Awareness in customer .....may or may not be target customers
5. Pricing of the product wrt to the competition

Going one by one
If its a new firm in the market place it will have to first create the footfalls at the outlets or Webspace (Whatever may be the platform) for its products. It can never hope to pick up trust from word of mouth .
So, ratings, comments and user guides are the only way out

If the product is old and the market share is less then there is some most likely some serious issue with the product and the company image in the market.......this may or may not be related to trust .....there may be some other issues like supplies and distribution ........for this the company need to set its house in order and look for the loop holes..............
if the product is better than word of mouth will be better option

Technical Level of the product may be out of the reach of the common customers .........here the company need to take advantage of this knowledge gap and take advantage of biased ratings, expert views, polls etc.

It may b possible that the product is priced above or below the market rate significantly ........in such a case the company can take advantage of the ratings better justifying both negative and positive pricings in its campaigns

Every position is different and need to be resolved by taking all the factors together ...........some may be stronger or some may be weaker as the case may be ...............

So, it need to be evaluated case to case basis.

I think a personal referral is always best. And ads/local interest stories may drum up interest but not necessarily clients.