The guide, which is available online, also details how to achieve Coeliac UK's gluten-free accreditation, which the charity said could help boost profits.
Sarah Sleet, chief executive of Coeliac UK, said: "Not only does gluten-free accreditation reassure customers that your food and kitchen are safe, it has a real impact on your bottom line too.
"It is estimated that the catering industry is missing out on £100m from people with coeliac disease and those they eat out with."
The UK market for gluten-free foods hit £184m last year and is growing 15% year-on-year, added Leon Mills, marketing manager at Knorr.
"As the demand for gluten-free grows, more and more familiar names like Pho and Côte Brasserie are getting accredited."
People with coeliac disease do not want to be made to feel different, he said.
"They want to be able to choose something from the menu that they trust has been prepared properly so they don't get sick. Gluten-free accreditation offers operators the opportunity to provide that reassurance."
Coeliac UK's gluten-free accreditation currently costs £175 for an audit and an additional, scaled fee to use the charity's gluten-free symbol, which is calculated based on businesses' net food sales turnover.
Symptoms of gluten intolerance can include bloating, weight loss, diarrhoea and anaemia.
Last year, a poll of the Publican's Morning Advertiser's (PMA) readers revealed that almost two thirds thought it was now absolutely necessary to cater for gluten-free customers.
Stosie Madi, chef-patron of the Parkers Arms, Newton-in-Bowland, Lancashire, said it just required a little bit of "thinking and prior planning".
"It's really important because people go out and talk about it and will recommend you," she said.
"They know they'll get something special and not just the bog-standard stuff thrown at them."
'May contain' warnings
The PMA recently reported that 'may contain' warnings on pub menus to alert customers that their food could possibly contain allergens like gluten might not be enough to protect operators from prosecution.
Speaking at the Institute of Food Safety Integrity & Protection's food law in practice conference, an industry expert, who could not be named due to reporting restrictions, said it was poor practice to expect consumers to be able to make their own risk assessments.