Live coverage of ad:tech San Francisco by David Shabelman.

ad:tech San Francisco is winding up, but attendance was still solid for a Q&A with Andy Cohen, CEO of elderly care Web site Caring.com , John Durham, CEO and managing partner of marketing services firm Catalyst SF and Will Price, CEO of Widgetbox.

Cohen told the audience that entrepreneurs must be persistent. He said entrepreneurs will always be giving reasons why they shouldn’t be doing something and constantly have setbacks. But he said if you can’t deal with rejection you shouldn’t be an entrepreneur. Durham concurred, saying, “don’t be afraid of failing.”

As for getting an audience with VCs, attendees were told it’s all about relationships. VCs will almost never take a meeting based on a cold call and typically talk to people they’ve worked with before or if they are introduced by someone they know or have worked with before.

Start-ups must be able to show the audience they are delivering, but traditional measuring services can often be costly. Instead, Cohen and Durham suggested publishers use Quantcast, an audience measuring service that’s gaining traction in the industry.

Despite some personal differences with p.r. firms in his career, Durham said in the digital space, public relations firms are important for start-ups to get their story out. Finding a blog writer to tell your story or good placement in a trade publication also are ways to gain attention.

Price ended the discussion by offering some hope to the entrepreneurs, saying he’s seen an improvement in conditions over the past couple of months and that the environment for starting a company is certainly better than it was at the end of 2009, when he said everyone feared they would be going out of business.

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